# AP Physics 2 : Other Circuit Principles

## Example Questions

### Example Question #1 : Other Circuit Principles

You have 4 resistors and an ammeter arranged as shown in the diagram below.

An ammeter measures current. The ammeter in this setup reads 0A. What is the resistance of ?

Possible Answers:

Correct answer:

Explanation:

This setup is called a Wheatstone bridge. It's used to find the resistance of a resistor with an unknown value. When the ammeter reads 0, the two sides are at equipotential, so

.

Therefore, the resistance of R is .

### Example Question #101 : Circuits

What is the resistance of a  long copper wire with a diameter of ?

Possible Answers:

Correct answer:

Explanation:

Write the following formula to find the resistance of the copper wire.

where  is the resistivity in  is the length of the wire in , and  is the cross sectional area of the wire in .

The resistivity of copper is: .

Substitute the givens to the resistance formula and solve.

### Example Question #3 : Other Circuit Principles

Determine the total resistance of the given circuit.

Possible Answers:

Correct answer:

Explanation:

In order to find the total resistance of the circuit, we need to combine all of the parallel resistors first, then add them together as resistors in series.

Combine  with :

Combine  with :

Combine  with :

Then, add the combined resistors, which are now all in series: