# High School Physics : Electricity and Magnetism

## Example Questions

### Example Question #1 : Calculating Total Resistance

Two resistors in series have  and  resistance, respectively. What is the total resistance?

Explanation:

For resistors in a series, total resistance is equal to the sum of each individual resistance.

We can use the individual resistances from the question to solve for the total resistance.

### Example Question #1 : Calculating Total Resistance

What is the total resistance of a series circuit with resistors of , and ?

Explanation:

For a series circuit, the formula for total resistance is:

We are given the values of each resistance, allowing us to sum them to find the total resistance in the circuit.

### Example Question #9 : Calculating Total Resistance

What is the total resistance of a parallel circuit with resistors of , and ?

Explanation:

The formula for resistance in parallel is:

We are given the values for each individual resistor, allowing us to solve for the total resistance.

### Example Question #10 : Calculating Total Resistance

Calculate the resistance of a copper wire with cross-sectional area of  and length of .

Explanation:

The resistance of a wire is given by the following equation:

We are given the resistivity (), cross-sectional area, and length. Using these values, we can solve for the resistance.

First, convert the cross-sectional area to square-meters.

Use the resistance equation to solve.

### Example Question #11 : Resistors

What is the total resistance of a , and  series circuit?

Explanation:

The formula for resistors in series is .

Plug in our given values.

### Example Question #1 : Resistors

There are three resistors in parallel in a circuit with resistances of , and .

What is the equivalent resistance?

Explanation:

The equation for resistors in parallel is:

We are given the values of the resistors. Using this formula, we can solve for the equivalent resistance.

Plug in the given values and solve.

### Example Question #41 : Electric Circuits

Which of these is the correct SI unit for capacitance?

Volts

Ohms

Newtons

Explanation:

The correct unit for capacitance is the Farad, named after the English physicist Michael Faraday.

Newtons are used to measure force. Ohms measure resistance and volts measure electrical energy or potential. Joules are a unit of energy, but Farad-Joules are not a recognizable unit.

### Example Question #2 : Capacitors

By using a dielectric, it is possible to store more energy in a capacitor. Why is this?

The dielectric replaces air, which breaks down when the electric fields get strong enough

The dielectric can store excess energy

The dielectric provides a direct energy source to the capacitor

The dielectric changes the distance between the two plates of the capacitor

The dielectric replaces air, which breaks down when the electric fields get strong enough

Explanation:

Dielectrics are insulating materials that can be polarized, and can be used to increase the separability of the two plates of a capacitor. When a dielectric is absent, air is present between the capacitor plates. At high voltages, when the electric field between the plates is incredibly strong, air begins to break down and becomes unable to prevent the flow of electricity between the capacitor plates. When this occurs, the capacitor cannot store energy, nor can it properly function. The presence of a dielectric eliminates this problem, allowing the capacitor to store much more energy.

### Example Question #1 : Calculating Total Capacitance

Three capacitors are in series. They have capacitances of , and , respectively. What is their total capacitance?

Explanation:

For capacitors in series the formula for total capacitance is:

Note that this formula is similar to the formula for total resistance in parallel. Using the values for each individual capacitor, we can solve for the total capacitance.

### Example Question #41 : Electric Circuits

Three capacitors are in parallel. They have capacitance values of , and . What is their total capacitance?