The Ultimate Oven Guide You Didn't Know You Needed (Part 1)
Theory of Electric and Microwave Ovens: Chapter 1
In this module, we will learn about:
- Ovens,
- Need of ovens,
- History of ovens, and
- The principle used in ovens.
We will also discuss the types of cooking and ovens. Skip to quiz!
Introduction to Ovens
An oven is a tool that exposes materials to a hot environment. The oven contains a hollow chamber and provides a means of heating the chamber in a controlled way. Ovens have been in use since ancient times in different forms and techniques.
Ovens have been used to achieve a wide variety of tasks requiring controlled heating. Ovens are of many different types like toasters, electric, and microwave ovens and are used for various purposes. Ovens differ depending on their use and based upon how they generate heat.
Cooking is a basic need of humans, and it can be achieved using various ways. Cooking requires heat to cook the food. The heat is generated from open fire cooking, gas stove, and heating elements in ovens.
Ovens are useful for a variety of cooking processes like
Baking,
Defrost,
Roasting,
Boiling, and many more.
In ovens, the food is cooked faster than the conventional methods. Modern day ovens are simple to use.
Ovens serves the purpose of:
Faster cooking,
Better cooking, and
Easier cooking.
The food is cooked evenly in the oven. While in a conventional method, the surface in contact with the heat is cooked first, than the others.
For example, heating a frozen food can take approximately half an hour on a gas stove. But when we cook it in a microwave oven, the frozen food gets heated in a few minutes. Now let us look at the history of ovens.
In the early part of the 19th century, coal ovens were used. It was cylindrical and made of heavy cast iron. The gas oven was used as early as the beginning of the 19th century. Gas oven became very common household cooking method, once gas lines were easily available to homes.
Electric ovens were invented by Canadian inventor Thomas Ahearn in the late 19th century. The popularity of the electric oven was slow to pick up due to the high prices of electricity. By the 1930s, when electricity became cheaper, electric stoves started gaining popularity.
In 1946, Dr. Percy Spencer discovered the heating properties of microwaves while studying the magnetron. By 1947, the first commercial microwave was in use in Boston, Mass. More recently, ovens have become slightly more high-tech in terms of cooking strategy.
The oven is a heating device that uses radiant heat generated by various sources. Radiant heat is a mechanism for heat transfer that does not require a medium in which it propagates. Radiant heat is generated by burning coal using gas burners, electrical coils, and radiation energy.
For example, humans are alive because radiant heat from the sun is available in abundance. Sun’s radiant heat interacts with the Earth, driving important environmental cycles and allowing life to flourish. Cooking is done using the radiant heat available from different sources.
Electric coils are heated using electrical energy and supplied in the required amount to cook the food. There are many electrical coils available depending on the type of material used, similar to filament bulbs.
The electromagnetic radiation transfer the energy at atom levels, the exchange of heat takes place between photons. The radiation energy in the form of microwaves is suitable for cooking purposes.
Cooking is the art of making food for consumption. Cooking is done in various methods and numerous processes, but some are used regularly for daily consumption. Each of these methods uses heat to cook foods differently.
Cooking can be of many types, but some of them are:
Baking,
Roasting,
Frying,
Grilling,
Steaming, and
Boiling.
As we are familiar with the above methods, we will look at the short description.
Baking is cooking food at lower temperatures; usually, cakes and bread are made using this process. Roasting is the process of cooking food evenly on all sides from an open flame or another heat source. It is best for cooking meat, roots, and mushroom-like vegetables.
Frying is cooking the food in an oil bath; often after, breading it, crispy food is made using this process. Broiling is the process of roasting the food from the above side, keeping the liquid as it is. Grilling is the process of cooking food, exposing directly to an open flame or coal.
Types of Ovens
Ovens are of many types, and ovens are categorized based on their:
Process,
Operation,
Heat transfer methods, and
Mounting type.
Let us see the types of the oven in each category.
Ovens based on their process are:
Earth oven,
Gas oven,
Brick oven,
Toaster oven,
Electric oven, and
Microwave oven.
Ovens based on their operation are:
Residential,
Commercial,
Industrial, and
Kiln.
Ovens based on their operation are:
Convectional heating,
Gas,
Electric, and
Radiation energy.
Ovens based on the mountings are:
Wall,
Double,
Slide-In,
Countertop,
Drop-In,
Freestanding, and
Drawer type.
Let us see about different types of ovens.
Earth oven: An earth oven is a pit dug into the ground and then heated by rocks or smoldering debris. Many cultures around the world have used Earth ovens for cooking. Ceramic oven: The ceramic oven is constructed of clay or other ceramic material and takes different forms depending on the culture.
Brick ovens are also another ceramic-type oven. A culture most notable for the use of brick ovens is Italy and its intimate history with pizza. Gas oven: An oven where the gas is used for cooking the food. It is the standard and basis for the modern gas oven.
Electric oven: These produce their heat electrically, often via resistive heating. It consists of a cabinet where the food is cooked. Toaster ovens are small electric ovens with a front door, wire rack, and removable baking pan. The bread is toasted in a toaster oven, the slices of bread are placed horizontally on the rack.
Masonry ovens consist of a baking chamber made of fireproof brick, concrete, stone, or clay. Modern masonry ovens are often fired with natural gas or even electricity and are closely associated with artisanal bread and pizza. Double oven: A built-in oven fixture with either two ovens or one electric oven and one microwave oven.
Wall ovens make it easier to work with large roasting pans and Dutch ovens. A wall oven mounted at the waist, or eye level is easier to use without bending. Steam oven: An oven that cooks food using steam to provide heat is a steam oven. The heat inside the oven turns the water into steam.
An oven is a tool to cook food using heat in a controlled way. Radiant heat is of many types, such as open fire, gas fire, electric heating, and radiation energy. Ovens cook different types of food faster than the conventional methods.
Components of Ovens
In this module, we will learn about the components of the oven. Skip to quiz!
List of Components
Ovens are of many types and consist of many components. However, electric and microwave ovens are commonly used today. We will discuss some of the general components which are found in most of the ovens.
Some of the ovens components are:
Broil element
Oven rack
Bake element
Convection fan
Convection oven fan blade
Convection oven Baffle
Light bulb
Hidden bake tray
Oven tube
Gas ignitor
Thermostat
Oven cavity
Heating Components
The broil element is typically found at the top of the oven cavity and provides direct heat to the top of food for broiling. The heating element works like a electric iron that produces heat when electricity passes through it. The heating element is an insulator which gets heated on the flow of current.
Recall that conductors allow electricity to flow easily but insulators do not. Both conductors and insulators provide resistance to the flow of electricity but in different amounts. A broiler element uses the resistance to produce heat that cooks the food.
For example, when walking on a crowded street, you have to spend more energy trying to dodge all the people and reach somewhere. This makes you spend more energy and your body heats up. Similarly a material with more resistance heat up as it wont allow electricity to pass easily.
Bake element is the primary heat source for most oven functions. It also consists of a heating element similar to the broil element.
The baking element is generally located at the bottom of the oven. The baking element is also frequently used for the self-cleaning feature in self-cleaning ovens. The bake element heats up the inside cavity of the oven, and the oil splatters and dust are loosened which can be cleaned easily with a clean cloth.
The hidden bake tray is located at the bottom of the oven cavity. The hidden bake tray protects the oven bake element from spills and drips that occur while cooking. It is advised to clean the hidden tray regularly to prevent any foul smell in the oven.
The oven rack holds cookware and bakeware inside the oven and can be moved up or down before cooking. The oven rack is similar to standard racks to keep more stuff within a confined space. The rack will expose the food to the heating element.
The racks will cook the food faster and more evenly. A broken or uneven oven rack can prevent food from cooking properly.
Fan Components
The convection fan circulates warm air around the oven cavity to help promote even cooking. The convection fan is usually found on the back wall of convection ovens. The heating elements are present on the top and bottom of the oven, so the heat needs to be circulated to cook the food evenly.
If the oven has a convection fan, the fan blade is a part of the oven's convection fan. The fan blade helps the fan create airflow throughout the oven. Fan blade helps in circulating the air inside the oven cavity to cook the food evenly.
Convection baffles encase the convection fan, typically located on the rear wall of the oven cavity. The convection fan consists of a blade, and it is needed to protect from any touches and food accumulating in it.
Other Components
The light bulb and assembly provide light inside the oven cavity and are often found on the top side. The bulb is linked to the door as the door opens; the light is switched on and closes when the door is closed. The proximity sensor helps in switching the light on and off.
The oven releases heat and moisture through the vent tube. It is usually found at the top of the oven cavity. When the food is cooked, the moisture present in the food is evaporated due to the heat. So, the vent tube helps the oven to keep it clean and moisture-free.
The gas oven ignitor, which is not found in electric ovens, ignites the oven’s heating burner. It’s typically located inside the oven and near the burner tube at the back.
The thermostat is a device that measures the temperature inside the oven’s cavity. The thermostat is connected to a capillary tube which consists of gas. The gas expands when there is a rise in temperature and is measured by the thermostat until the desired temperature is achieved.
The expanded gas disconnects the contactor pushing the bellow. Then the contactor disconnects the electrical connection stopping the heating element from heating. The cycle is repeated to obtain the required temperature in the oven.
The oven consists of a wide of parts that are useful in operation. Heating elements help in cooking the food. The thermostat is the main component by which the temperature is maintained inside the oven.
Electric oven
In this module, we will learn the details of an electric oven. We will learn:
- What an electric oven is,
- How it works, and
- Uses of an electric oven. Skip to quiz!
Introduction to Electric Oven
An oven that uses electrical energy to heat the food is known as an electric oven. The electric oven uses electrical energy, and it converts the electricity into heat using heating elements. The electric oven has multiple cooking methods as per the heating method used in it.
An oven's functions increase when there are two or more heating elements. Nowadays, electric ovens are also known as conventional ovens. The electric oven has racks, a convection fan, heating elements, and knobs to set the temperature and cook time.
The principle used in an electric oven is electrical energy. An electric oven produces heat electrically using a heating element in the form of coils and tubes. The heating element converts electrical energy into heat through the process of resistance.
Nowadays, the electric oven consists of an Electronic Printed Circuit (PC) board and is known as an Electronic oven. The electronic oven is an oven with a PC board/timer assembly with relays onto the board.
Components of an Electric Oven
The main components of an electric oven are
Cabinet,
Heating element,
Thermostat,
Timer, and
Power regulating switch.
Let us see the working of each component.
The oven cabinet is the outer metallic body of the oven. The metal box body is composed of
an outer shell,
a middle layer, and
an inner container.
The three-layer structure forms a separate air cavity between the inner layer’s front and back sides.
An insulating expanded perlite product is filled in the outer cavity. The insulating material helps to reduce the outer shell's temperature and prevents it from heating. Similar to a thermo-flask which has multiple layers to keep the tea or coffee hot for a longer time.
A spring structure is arranged below the door to cause the door to be pressed on the door frame at all times to have better sealing properties. This prevents the oven cavity to do not lose any heat and it is sealed from the outside air.
Recall that the broil element is typically found at the top of the oven cavity and provides direct heat to the top of food for broiling. A broiler is a section that provides high, direct heat like a grill.
Broiling places food close to the oven’s heating element so that it can quickly cook, brown, char, or caramelize. Broil elements can give food more complex flavors or help you achieve certain textures.
A thermostat is a device that measures the temperature inside the oven’s cavity. A thermostat is similar to a thermometer that can measure very high temperatures in an oven.
The thermostat is connected to a capillary tube which consists of gas. The gas expands when there is a rise in temperature until the desired temperature is achieved.
Working of an Electric Oven
The electric oven consists of a control board, temperature sensor, broil element, and bake element. The user provides the temperature and time. The control board sends the 120V current to both the broil and bake heating element.
The oven is preheated, and the control board monitors the temperature sensor using an oven control thermostat. The cycle is repeated and controlled by the control board until the desired temperature is achieved.
The broil setting uses broil elements only. Both the elements are used in the bake setting, and the bake element generates most of the heat. A convection oven fan circulates the heat all around the oven to bake or cook the food evenly.
Use of an Electric Oven
Ovens use electricity and can heat to a very high temperature. So it is not advisable to leave the food cooking in the oven unattended. Don’t use the oven as a storage cupboard – someone might forget and turn it on. Make sure to keep the oven clean from grease and splatters of food that can catch fire.
Never use water on a kitchen grease fire; use a wet cloth to extinguish the fire. Keep oven gloves, tea towels, and other flammable materials away from the oven. Always turn off the oven when not in use and read the owner’s manual before using the oven.
The general method to cook using an electric oven is:
Check the recipe for an electric oven with recommended time and temperature.
Adjust the temperature knob.
Adjust the time knob.
Preheat the oven.
Use cook methods like bake, broil, grill, and roast.
Take out the cooked food.
The electric oven can be classified as
Conventional oven, and
Convection oven
The convection oven uses a fan to circulate the heat, which is the only difference between them. Let us look at a video for the difference.
An oven that uses electrical energy to heat the food is known as an electric oven. The main components of an electric oven are
Cabinet,
Heating element,
Thermostat,
Timer, and
Power regulating switch.
An electric oven uses electrical energy to cook the food, so all the necessary safety has to be followed while using it. For operating the oven, read the user manual first, then proceed with cooking. The electric ovens are of two types: a conventional oven and a convection oven, which consists of a fan.
Microwave oven
In this module, we will learn the details of a microwave oven. We will learn:
- What a microwave oven is,
- How it works, and
- Use of a microwave oven.
Introduction to Microwave Oven
An oven that cooks food using microwave radiation is known as a microwave oven. Microwave ovens heat food using microwaves, a form of electromagnetic radiation similar to radio waves.
A device called a magnetron inside the oven produces microwaves. Microwaves reflect off the metal interior of the oven and cause the water molecules to vibrate in the food. The vibration results in friction between molecules that produce heat which cooks the food.
Generating Microwaves
The magnetron is a high-powered vacuum tube that produces microwaves. Due to the discovery of magnetron, we are now able to use microwave ovens. Let us see a video to understand how magnetron works.
As seen in the video, a series of operations takes place before the microwaves are generated. For example, the wifi router produces radio waves which are used to connect the mobiles and Laptops. Similarly, a magnetron produces microwaves which are used for cooking food.
The magnetron is a device that is commonly used in different military applications like radars. The desired range and frequencies of waves are obtained by the amount of power supplied to the magnetron. Let us see the properties of microwaves.
Microwaves are a form of electromagnetic radiation. Electromagnetic radiation spans a broad spectrum, and microwaves fall in between the range of 1 gigahertz (GHz) to 300 GHz. The human eye can only see a small portion of this spectrum called visible light, and its range is 400–790 terahertz (THz).
Microwaves have three characteristics that allow them to be used in cooking. The characteristics of microwaves are:
Reflected by metal,
Pass through glass, paper, plastic, and
Some materials and foods absorb them.
The resonance cavity reflects the microwaves produced by the magnetron. A resonance cavity is an electronic device consisting of a space usually enclosed by metallic walls. A microwave is reflected multiple times to achieve a final resonant wave.
A resonant wave in a resonance cavity is oscillating. The oscillating waves with the same amplitude combine to become a giant wave. Recall amplitude is the distance from the centerline (or the still position) to the maximum peak or decline in a wave.
Waves generated can have multiple amplitudes, and the resonance cavity help to generate high amplitude waves. The waves which have a high amplitude possess high energy, so these are suitable for heating.
The standing wave created in a resonance cavity has different intensities at different spots. This creates uneven cooking all around the food, where the waves have higher energy. The waves at these spots cook the food first, and these are known as hotspots.
A rotating plate was invented to overcome this problem. As the microwaves oscillate within the cavity and at specified locations, a rotating plate helps to cook the food evenly. The rotating plates help the food to get heated all round exposed to the waves.
The electronic control is responsible for the microwaves generated by the magnetron. The magnetron is driven by a linear transformer which can be easily switched on or off completely. Recall that the transformer is a device that either increases or decreases the voltage supply in the circuit.
The power level doesn't affect the intensity of the microwave radiation, but the magnetron is cycled on and off every few seconds. This switching helps to achieve the required amount of heat and faster cooking.
Working of a Microwave Oven
Control panels feature an LED, liquid crystal, or vacuum fluorescent display, numeric buttons for entering the cooking time, and power level selection. Some consist of function buttons such as a defrost setting and pre-programmed settings for different food types, such as meat, poultry, vegetables, frozen dinners, and many more.
Power settings are commonly implemented, not by varying the effect but by repeatedly turning the power off and on. The highest power setting thus represents continuous power. For example, A defrost might represent power for two seconds followed by no power for five seconds.
To indicate cooking has been completed, an audible warning such as a bell or a beeper is usually present. Usually, "End" appears on the display of a digital microwave when the food is cooked.
Inside the strong metal box, there is a microwave generator called a magnetron. The magnetron takes electricity from the power outlet and converts it into high-powered microwaves when pressed start. The magnetron sends these waves into the food compartment through a channel called a waveguide.
The food sits on a rotating table, spinning slowly around, so the microwaves cook it evenly. The microwaves bounce back and forth off the reflective metal walls of the food compartment, just like light bounces off a mirror. When the microwaves reach the food, they don't simply bounce off, it penetrates.
As radio waves can pass straight through the walls of your house, so microwaves penetrate inside the food. As microwaves travel through the food, they make the molecules inside it vibrate more quickly. Vibrating molecules generate heat, so the food becomes hotter, and it gets cooked.
Use of a Microwave Oven
Use only microwave-safe cookware specially manufactured for use in the microwave oven. Don't operate a microwave oven if the door does not close firmly or is bent, warped, or damaged. Regularly clean the oven cavity, the outer edge of the cavity, and the door with water and a mild detergent.
Stop using a microwave oven if it continues to operate with the door open. Don't stand directly against an oven (and don't allow children to do this) for long periods while it is operating. Do not heat water or liquids in the microwave oven longer than the recommended time.
The ovens should not be operated when empty and if there is no door seal. Be sure not to use scouring pads, steel wool, or other abrasives to clean the oven. Follow the manufacturer's instruction manual for recommended operating procedures and safety precautions for your oven model.
Each oven has signs on it which material must be used while cooking, and no other material can be used. Metal bowls can’t be used for cooking as the radiation penetrates through them. While using metal bowls with sharp edges may cause sparks and flashes.
High amounts of radiation exposure from the oven can cause skin burns. Overheating of the food may be quickly done in the oven so that handling issues may be present. Closed items, such as eggs, can explode when heated in a microwave oven due to the increased pressure from steam.
An oven that cooks food using microwaves is known as a microwave oven. A magnetron generates microwaves, and the resonance cavity helps create longer waves that cook food. Microwave ovens are hazardous when not used in prescribed ways.
Question #1: The oven contains a hollow chamber and provides a means of heating the chamber in a _______ way.
Open
Better
Controlled
Uncontrolled
Scroll down for the answer...
Answer: Controlled
The oven contains a hollow chamber and provides a means of heating the chamber in a controlled way.
Question #2: In ovens, the food is cooked _____ than the conventional methods.
Slower
Delayed
Faster
Equal
Scroll down for the answer...
Answer: Faster
In ovens, the food is cooked faster than the conventional methods.
Question #3: Dr. Percy Spencer discovered the heating properties of _______ while studying the magnetron.
Laser light
Air
Light
Microwaves
Scroll down for the answer...
Answer: Microwaves
Dr. Percy Spencer discovered the heating properties of microwaves while studying the magnetron.
Question #4: Electric coils are heated using _____ and supplied in the required amount to cook the food.
Radiation energy
Hydro energy
Electrical energy
Wind energy
Scroll down for the answer...
Answer: Electrical energy
Electric coils are heated using electrical energy and supplied in the required amount to cook the food. There are many electrical coils available depending on the type of material used, similar to filament bulbs.
Question #5: The art of making food for consumption is?
Cooking
Frying
Baking
Roasting
Scroll down for the answer...
Answer: Cooking
Cooking is the art of making food for consumption. Cooking is done in various methods and numerous processes, but some are used regularly for daily consumption.
Question #6: Ovens based on the mountings are: (Select all that apply)
Electric
Wall
Industrial
Countertop
Scroll down for the answer...
Answer: Wall
Countertop
Ovens based on the mountings are:
Wall,
Double,
Slide-In,
Countertop,
Drop-In,
Freestanding, and
Drawer type.
Question #7: A built-in oven fixture with either two ovens or one electric oven and one microwave oven is known as
Drawer
Slide-in oven
Microwave oven
Double oven
Scroll down for the answer...
Answer: Double oven
Double oven: A built-in oven fixture with either two ovens or one electric oven and one microwave oven.
Question #8: Oven components are: (Select all that apply)
Bake element
Engine
Convection Fan
Table
Scroll down for the answer...
Answer: Bake element
Convection Fan
Ovens components are:
Broil element
Oven rack
Bake element
Convection fan
Convection oven fan blade
Convection oven Baffle
Light bulb
Hidden bake tray
Oven tube
Gas ignitor
Thermostat
Question #9: Broil element converts electrical energy into heat through the process of _____
Conductance
Heating
Resistance
Transfer
Scroll down for the answer...
Answer: Resistance
Broil element converts electrical energy into heat through the process of resistance.
Question #10: Bake element is the _____ heat source for most oven functions.
Primary
Unnecessary
Secondary
None of the above.
Scroll down for the answer...
Answer: Primary
Bake element is the primary heat source for most oven functions.
Question #11: Convection fan helps to circulate the warm air and to cook the food _____
Partially
Evenly
At required places
One side
Scroll down for the answer...
Answer: Evenly
Convection fan helps to circulate the warm air and to cook the food evenly.
Question #12: The light bulb assembly turns off the light when the door is ______
Partially open
Open
Kept in middle
Closed
Scroll down for the answer...
Answer: Closed
The light bulb and assembly provide light inside the oven cavity and are often found on the top side. The light bulb assembly turns off the light when the door is closed.
Question #13: The thermostat is connected to a capillary tube which consists of ____.
Air
Water
Gas
Refrigerant
Scroll down for the answer...
Answer: Gas
The thermostat is connected to a capillary tube which consists of gas.
Question #14: An electric oven uses electrical energy, and it converts the electricity into heat using _____.
Heating element
Door
Convection Fan
Cabinet
Scroll down for the answer...
Answer: Heating element
The electric oven uses electrical energy, and it converts the electricity into heat using heating elements.
Question #15: The heating element in an electric oven converts electrical energy into heat through the process of ______
Conductance
Current
Resistance
Heating
Scroll down for the answer...
Answer: Resistance
The heating element in an electric oven converts electrical energy into heat through the process of resistance.
Question #16: The electric oven comprises of (Select all that apply)
Stove
Cabinet
Battery
Thermostat
Scroll down for the answer...
Answer: Cabinet
Thermostat
The electric oven comprises of a
Cabinet,
Heating element,
Thermostat,
Timer, and
Power regulating switch.
Question #17: In an electric oven metal box body is composed of?
Outer shell
Middle layer
Inner container
All of the above
Scroll down for the answer...
Answer: All of the above
In an electric oven the metal box body is composed of
an outer shell,
a middle layer, and
an inner container.
Question #18: The broil element is typically found at the top of the oven cavity and provides ______ heat to the top of food for broiling.
Continuous
Transfer
No
Direct
Scroll down for the answer...
Answer: Direct
The broil element is typically found at the top of the oven cavity. It provides direct heat to the top of food for broiling.
Question #19: The thermostat is connected to a capillary tube which consists of ____.
Mercury
Gas
Air
Water
Scroll down for the answer...
Answer: Gas
The thermostat is connected to a capillary tube which consists of gas.
Question #20: When the user sets a timer and required temperature, then which elements get heated?
Thermostat
Oven cavity
Convection Fan
Bake and broil element
Scroll down for the answer...
Answer: Bake and broil element
When the user provides the temperature and time, the control board sends the 120V to the broil and bake heating element.
Question #21: Always turn off the oven when not in use. (Select true or false)
True
False
Scroll down for the answer...
Answer: True
Always turn off the oven when not in use. Read the owner’s manual before using the oven.
Question #22: Never use ____ on a kitchen grease fire; use a wet cloth to extinguish the fire.
Air
Water
Utensils
Fan
Scroll down for the answer...
Answer: Water
Make sure to keep the oven clean from grease and splatters of food that can catch fire. Never use water on a kitchen grease fire; use a wet cloth to extinguish the fire.
Question #23: The main difference between a conventional oven and a convection oven is a ____.
Bake element
Heater
Fan
Tray
Scroll down for the answer...
Answer: Fan
The main difference between a conventional oven and a convection oven is the fan. A convection fan helps in cooking the food evenly.
Question #24: Which device is responsible to produce microwaves inside the microwave oven?
Thermostat
Electron
Magnetron
Light bulb
Scroll down for the answer...
Answer: Magnetron
A device called a magnetron inside the oven produces microwaves in the microwave oven.
Question #25: The desired range and frequencies of waves are obtained by controlling the _____ supplied to the magnetron.
Power
Light
Coil
Water
Scroll down for the answer...
Answer: Power
The desired range and frequencies of waves are obtained by controlling the power supplied to the magnetron.
Question #26: The characteristics of microwaves are: (Select all that apply)
Reflected by metal
Switch on the light
Some materials and foods absorb them
Provide X-ray images
Scroll down for the answer...
Answer: Reflected by metal
Some materials and foods absorb them
The characteristics of microwaves are:
Reflected by metal,
Pass through glass, paper, plastic, and
Some materials and foods absorb them.
Question #27: In a resonance cavity, a microwave is______ multiple times to achieve a final resonant wave.
Refracted
Stopped
Transmitted
Reflected
Scroll down for the answer...
Answer: Reflected
In a resonance cavity, a microwave is reflected multiple times to achieve a final resonant wave.
Question #28: As the microwaves oscillate within the cavity and at specified locations, a rotating plate helps to cook the food _____.
Partially
Evenly
At required places
One side
Scroll down for the answer...
Answer: Evenly
As the microwaves oscillate within the cavity and at specified locations, a rotating plate helps to cook the food evenly.
Question #29: Closed items, such as eggs, can ______ when heated in a microwave oven due to the increased pressure from steam.
Explode
Break
Cook easily
Damage
Scroll down for the answer...
Answer: Explode
Closed items, such as eggs, can explode when heated in a microwave oven due to the increased pressure from steam.