This Physics quiz is called 'Electricity - Current, Charge and Power' and it has been written by teachers to help you if you are studying the subject at senior high school. Playing educational quizzes is one of the most efficienct ways to learn if you are in the 11th or 12th grade - aged 16 to 18.
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Knowing how current, charge and power are calculated is extremely helpful in senior high school Physics when considering electrical circuits. In everyday life, there is a wide choice of electrical appliances available to buy. They are all designed to transfer electrical energy into other forms of energy, but not all appliances are as efficient as one another.
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Knowing how current, charge and power are related can help you decide when you are buying. It can also help you with safety in the home as you can work out the current that each one will draw when running at full power. So how is this useful? You can work out the correct size of fuse to use and also make sure that an extension lead or household circuit is not being overloaded.
Electricity is a flow of electrons through a material. Electrons carry a very small amount of electrical charge but since they are extremely tiny, there are massive numbers of them on the move in a working circuit. One coulomb equals the negative of the charge of 6.24 x 1018 electrons. Using the coulomb avoids needing to use this large number in calculations. In equations, charge is represented by q (or Q) and has the SI unit symbol C.
Electrical current is the rate of flow of this charge in a circuit. It has the symbol I in equations and is measured in amperes (usually shortened to 'amps') which has the SI unit symbol of A. The current flowing round a circuit is measured using an ammeter. One amp is equivalent to one coulomb of electricity passing a given point in a circuit in one second.
Power refers to how fast energy is transferred, so you can calculate the power consumption (in watts) of an electrical appliance by dividing the energy transferred (in joules) by the time taken to transfer that amount of energy in seconds. One of the common mistakes made in senior high school is to forget to convert time into seconds. Power is directly related to the current and the potential difference, if you multiply the curent in amps by the potential difference in volts, you have the power of an appliance. In the exams, when asked about electricity you will often need to rearrange these relationships (or even combine them) to calculate the figure demanded in the question, so make sure that you revise the basic equations related to current charge and power thoroughly.
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1.
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If a charge flows through a resistor, which of the following happens to the resistor? |
|
[ ] |
It gets colder |
[ ] |
It gets hotter |
[ ] |
It becomes positively charged |
[ ] |
Nothing |
|
|
2.
|
In a filament lamp, in what form is most of the energy lost? |
|
[ ] |
Heat |
[ ] |
Sound |
[ ] |
Kinetic energy |
[ ] |
Radio waves |
|
|
3.
|
What is power? |
|
[ ] |
The number of repetitions of squats a body-builder can perform |
[ ] |
The number of cylinders in a car |
[ ] |
The rate at which energy is absorbed |
[ ] |
The rate at which energy is transferred |
|
|
4.
|
What is the formula for power? |
|
[ ] |
P = E⁄t |
[ ] |
P = t⁄E |
[ ] |
P = E⁄2t |
[ ] |
P = 2E⁄t |
|
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5.
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Calculate the power of an appliance that uses 1000 joules of energy in 5 seconds. |
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[ ] |
100 W |
[ ] |
200 W |
[ ] |
300 W |
[ ] |
400 W |
|
|
6.
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Power, potential difference and current are correctly related by which equation? |
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[ ] |
P = I x V |
[ ] |
P = 2I x V |
[ ] |
P = I⁄V |
[ ] |
P = I⁄2V |
|
|
7.
|
What is the voltage of an appliance if it uses 200 J per second when supplied with a current of 5 A? |
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[ ] |
10 V |
[ ] |
20 V |
[ ] |
30 V |
[ ] |
40 V |
|
|
8.
|
Which equation correctly shows the relationship between energy transferred, voltage and charge? |
|
[ ] |
E = V x Q |
[ ] |
E = 2V x Q |
[ ] |
E = V⁄Q |
[ ] |
E = Q⁄V |
|
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9.
|
What is the energy transferred if the voltage is 5 V and the charge is 10 C? |
|
[ ] |
50 |
[ ] |
25 |
[ ] |
50 J |
[ ] |
25 J |
|
|
10.
|
What size of fuse would be required for a 230 V, 500 W heater? |
|
[ ] |
3 A |
[ ] |
5 A |
[ ] |
13 A |
[ ] |
1 A |
|
|
1.
|
If a charge flows through a resistor, which of the following happens to the resistor? |
|
[ ] |
It gets colder |
[x] |
It gets hotter |
[ ] |
It becomes positively charged |
[ ] |
Nothing |
|
|
2.
|
In a filament lamp, in what form is most of the energy lost? |
|
[x] |
Heat |
[ ] |
Sound |
[ ] |
Kinetic energy |
[ ] |
Radio waves |
|
|
3.
|
What is power? |
|
[ ] |
The number of repetitions of squats a body-builder can perform |
[ ] |
The number of cylinders in a car |
[ ] |
The rate at which energy is absorbed |
[x] |
The rate at which energy is transferred |
|
|
4.
|
What is the formula for power? |
|
[x] |
P = E⁄t |
[ ] |
P = t⁄E |
[ ] |
P = E⁄2t |
[ ] |
P = 2E⁄t |
|
|
5.
|
Calculate the power of an appliance that uses 1000 joules of energy in 5 seconds. |
|
[ ] |
100 W |
[x] |
200 W |
[ ] |
300 W |
[ ] |
400 W |
|
|
6.
|
Power, potential difference and current are correctly related by which equation? |
|
[x] |
P = I x V |
[ ] |
P = 2I x V |
[ ] |
P = I⁄V |
[ ] |
P = I⁄2V |
|
|
7.
|
What is the voltage of an appliance if it uses 200 J per second when supplied with a current of 5 A? |
|
[ ] |
10 V |
[ ] |
20 V |
[ ] |
30 V |
[x] |
40 V |
|
|
8.
|
Which equation correctly shows the relationship between energy transferred, voltage and charge? |
|
[x] |
E = V x Q |
[ ] |
E = 2V x Q |
[ ] |
E = V⁄Q |
[ ] |
E = Q⁄V |
|
|
9.
|
What is the energy transferred if the voltage is 5 V and the charge is 10 C? |
|
[ ] |
50 |
[ ] |
25 |
[x] |
50 J |
[ ] |
25 J |
|
|
10.
|
What size of fuse would be required for a 230 V, 500 W heater? |
|
[x] |
3 A |
[ ] |
5 A |
[ ] |
13 A |
[ ] |
1 A |
|
|