AP Physics 1 : Electricity and Waves

Study concepts, example questions & explanations for AP Physics 1

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Example Questions

Example Question #175 : Electricity

If a  lightbulb has a resistance of , how much current is going across the lightbulb?

Possible Answers:

Correct answer:

Explanation:

The power in a circuit is determined by the equation , where  is the power of the circuit,  is the current in the circuit, and  is the equivalent  resistance of the circuit.

Solving the power equation for current gives 

In this problem, 

Example Question #251 : Electricity And Waves

How much energy does a  lightbulb give off in ?

Possible Answers:

Not enough information

Correct answer:

Explanation:

Energy is related to power by the equation , where  is energy,  is the power of the circuit, and  is time.

Time needs to be in seconds.

For our problem, energy is

Example Question #252 : Electricity And Waves

What is the circuit power of a circuit with a battery with potential difference , and 3 resistors in parallel with equivalent resistances of 

Possible Answers:

Correct answer:

Explanation:

Recall the formula for circuit power:

 

We know that . To determine resistance of 3 resistors in parallel we set up the equation for total resistance for resistors in parallel:

From our formula we know that the circuit power is:

Example Question #183 : Electricity

Consider a series circuit with a  battery. The circuit is composed of three resistors, . Calculate the power  (units of Watts ) of the circuit.

Possible Answers:

Correct answer:

Explanation:

We can write the power of a circuit as: 

This however, does not help much because we do not know the current in the circuit. But by Ohm's law: 

Substitution of this expression into the expression for power gives us:

Where , the total resistance of the circuit. For a circuit in series, the total resistance is simply the sum of the resistors:

 

Therefore, the power of the circuit is:

Example Question #184 : Electricity

Calculate the power  of a circuit composed of a  battery and three resistors in parallel. The resistors have resistance values of 

Possible Answers:

Correct answer:

Explanation:

The power  of a circuit is given by:

.

By substitution of Ohm's law, we can show that:

Where , or the total resistance of the circuit. For resistors in parallel, we add the inverses of their values. This is shown more plainly as: 

 

From the given values, we can calculate the total resistance as . This leads us to the final answer:

Example Question #141 : Circuits

You are given the following circuit powered by a  battery:

Circuit

Find the power supplied by the battery.

Possible Answers:

Correct answer:

Explanation:

The power provided by the battery is equal to the product of the current that passes through it and the voltage it provides. In order to find the current, you must find the equivalent resistance of the circuit.

Since R1 is in series with R2 and R3, who are in parallel, the equivalent resistance is given by: 

Then, to find power, you can use the following formula:

The battery supplies  of power.

Example Question #254 : Electricity And Waves

How much power does a circuit produce if there is an equivalent resistance of  and a current of ?

Possible Answers:

Correct answer:

Explanation:

The equation for power in a circuit is given as:

 is the power in Watts,  is the current in amps, and  is the resistance in ohms. By solving the equation and substituting our values, we obtain:

Example Question #187 : Electricity

A capacitor with a capacitance of  stores  of energy. What is the voltage across this capacitor?

Possible Answers:

Correct answer:

Explanation:

The correct answer is .

We can obtain this answer with the following equation regarding capacitors:

 is the energy stored on the capacitor,  is the capacitance, and  is the voltage.

Solving for  we obtain:

Example Question #255 : Electricity And Waves

What is the power of a circuit with a resistance of  and  current?

Possible Answers:

Correct answer:

Explanation:

We calculate the power in a circuit using the following equation

Given  and 

Example Question #189 : Electricity

What is the power of a circuit with a resistance of  and  current?

Possible Answers:

Correct answer:

Explanation:

We calculate the power in a circuit using the following equation

Given  and 

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