# Test Prep

### Multiple Choice

#### 19.1 Ohm's Law

- $\text{C/s}$
- $\text{e/s}$
- $-\text{e}/\text{s}$
- ${\text{C/s}}^{2}$

- $\text{C/m}$
- $\text{C/s}$
- $\mathrm{\Omega}$
- $\mathrm{\Psi}$

The equivalent unit for an ohm is a ________.

- V/A
- C/m
- $$\frac{\text{A}}{\text{V}}$$
- V/s

- 1
- $\frac{1}{2}$
- 4
- 2

#### 19.2 Series Circuits

- a battery
- a capacitor
- the ground
- a switch

How many 10-Ω resistors must be connected in series to make an equivalent resistance of 80 Ω?

- 80
- 8
- 20
- 40

- a battery connected in series with an inductor
- a capacitor connected in series with a resistor
- a resistor connected in series with a battery
- an inductor connected in series with a resistor

How much current will flow through a 10-V battery with a 100-Ω resistor connected across its terminals?

- 0.1 A
- 1.0 A
- 0
- 1,000 A

#### 19.3 Parallel Circuits

A 10-Ω resistor is connected in parallel to another resistor R . The equivalent resistance of the pair is 8 Ω. What is the resistance R?

- 10 Ω
- 20 Ω
- 30 Ω
- 40 Ω

- The resistors are connected in parallel because the same current flows through all three resistors.
- The resistors are connected in parallel because different current flows through all three resistors.
- The resistors are connected in series because the same current flows through all three resistors.
- The resistors are connected in series because different current flows through all three resistors.

#### 19.4 Electric Power

- $$P={I}^{2}R$$
- $P=\frac{V}{{R}^{2}}$
- $$P=IV$$
- $P=\frac{{V}^{2}}{R}$

- $$0.36\phantom{\rule{thinmathspace}{0ex}}\text{W}$$
- $0.011\phantom{\rule{thinmathspace}{0ex}}\text{W}$
- $5\phantom{\rule{thinmathspace}{0ex}}\text{V}$
- $2.5\phantom{\rule{thinmathspace}{0ex}}\text{W}$

- A resistor dissipates power in the form of heat.
- A resistor dissipates power in the form of sound.
- A resistor dissipates power in the form of light.
- A resistor dissipates power in the form of charge.

### Short Answer

#### 19.1 Ohm's Law

True or false—it is possible to produce nonzero DC current by adding together AC currents.

- false
- true

What type of current is used in cars?

- alternating current
- indirect current
- direct current
- straight current

- $C=Bg$
- $g=BC$
- $\frac{B}{C}=\frac{C}{g}$
- $B=Cg$

- Ohm’s law says that the current through a resistor equals the voltage across the resistor multiplied by the resistance of the resistor.
- Ohm’s law says that the voltage across a resistor equals the current through the resistor multiplied by the resistance of the resistor.
- Ohm’s law says that the resistance of the resistor equals the current through the resistor multiplied by the voltage across a resistor.
- Ohm’s law says that the voltage across a resistor equals the square of the current through the resistor multiplied by the resistance of the resistor.

What is the current through a 100-Ω resistor with 12 V across it?

- 0
- 0.12 A
- 8.33 A
- 1,200 A

- $0.017$
- 1
- 60
- 120

#### 19.2 Series Circuits

Given a circuit with one 9-V battery and with its negative terminal connected to ground. The two paths are connected to ground from the positive terminal: the right path with a 20-Ω and a 100-Ω resistor and the left path with a 50-Ω resistor. How much current will flow in the right branch?

- $$\frac{\text{9}}{\text{120}}$$
- $$\frac{\text{9}}{\text{100}}$$
- $$\frac{\text{9}}{\text{50}}$$
- $$\frac{\text{9}}{\text{20}}$$

- All of the current flows through the left branch due to the open switch.
- All of the current flows through the right branch due to the open switch in the left branch.
- All of the current flows through the middle branch due to the open switch in the left branch
- There will be no current in any branch of the circuit due to the open switch.

- $0.072\phantom{\rule{thinmathspace}{0ex}}\text{A}$
- $0.12\phantom{\rule{thinmathspace}{0ex}}\text{A}$
- $0.18\phantom{\rule{thinmathspace}{0ex}}\text{A}$
- $0.3\phantom{\rule{thinmathspace}{0ex}}\text{A}$

- $$0.028\phantom{\rule{thinmathspace}{0ex}}\mathrm{\Omega}$$
- $$2.25\phantom{\rule{thinmathspace}{0ex}}\mathrm{\Omega}$$
- $$36\phantom{\rule{thinmathspace}{0ex}}\mathrm{\Omega}$$
- $72\phantom{\rule{thinmathspace}{0ex}}\mathrm{\Omega}$

#### 19.3 Parallel Circuits

Ten 100-Ω resistors are connected in series. How can you increase the total resistance of the circuit by about 40 percent?

- Adding two 10-Ω resistors increases the total resistance of the circuit by about 40 percent.
- Removing two 10-Ω resistors increases the total resistance of the circuit by about 40 percent.
- Adding four 10-Ω resistors increases the total resistance of the circuit by about 40 percent.
- Removing four 10-Ω resistors increases the total resistance of the circuit by about 40 percent.

- The current and the voltage remain the same.
- The current decreases and the voltage remains the same.
- The current and the voltage increases.
- The current increases and the voltage remains the same.

- The most current flows through the 15-Ω resistor because all the current must pass through this resistor.
- The most current flows through the 20-Ω resistor because all the current must pass through this resistor.
- The most current flows through the 25-Ω resistor because it is the highest resistance.
- The same current flows through the all the resistor because all the current must pass through each of the resistors.

#### 19.4 Electric Power

You want to increase the power dissipated in a circuit. You have the choice between doubling the current or doubling the resistance, with the voltage remaining constant. Which one would you choose?

- doubling the resistance
- doubling the current

You want to increase the power dissipated in a circuit. You have the choice between reducing the voltage or reducing the resistance, with the current remaining constant. Which one would you choose?

- reduce the voltage to increase the power
- reduce the resistance to increase the power

What power is dissipated in the circuit consisting of 310-Ω resistors connected in series across a 9.0-V battery?

- The power dissipated is 2430 W.
- The power dissipated is 270 W.
- The power dissipated is 2.7 W.
- The power dissipated is 0.37 W.

What power is dissipated in a circuit consisting of three 10-Ω resistors connected in parallel across a 9.0-V battery?

- The power dissipated is 270 W.
- The power dissipated is 30 W.
- The power dissipated is 24 W.
- The power dissipated is 1/24 W.

### Extended Response

#### 19.1 Ohm's law

- Electric current is the charge that passes through a conductor per unit time. The direction of the current is defined to be the direction in which positive charge would flow.
- Electric current is the charges that move in a conductor. The direction of the current is defined to be the direction in which positive charge would flow.
- Electric current is the charge that passes through a conductor per unit time. The direction of the current is defined to be the direction in which negative charge would flow.
- Electric current is the charges that move in a conductor. The direction of the current is defined to be the direction in which negative charge would flow.

- If small amount of current flows through a resistor, the resistor will heat up so much that it will change state, in violation of Ohm’s law.
- If excessive amount of current flows through a resistor, the resistor will heat up so much that it will change state, in violation of Ohm’s law.
- If small amount of current flows through a resistor, the resistor will not heat up so much and it will not change its state, in violation of Ohm’s law.
- If excessive amount of current flows through a resistor, the resistor will heat up so much that it will not change its state, in violation of Ohm’s law.

- $\frac{R}{10}$
- $5\phantom{\rule{thinmathspace}{0ex}}\text{R}$
- $\frac{10}{R}$
- $10\phantom{\rule{thinmathspace}{0ex}}\text{R}$

#### 19.2 Series Circuits

- If the current were not constant, the mobile charges would bunch up in places, which means that the voltage would decrease at that point. A lower voltage at some point would push the current in the direction that further decreases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which means that the voltage would increase at that point. But a higher voltage at some point would push the current in the direction that decreases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which mean that the voltage would increase at that point. A higher voltage at some point would push the current in the direction that further increases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which mean that the voltage would decrease at that point. But a lower voltage at some point would push the current in the direction that increases the voltage.

What is the current through each resistor in the circuit?

- Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and*R*_{4}is 0.48 A, 0.30 A, 1.2 A, and 0.24 A, respectively. - Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and*R*_{4}is 1200 A, 1920 A, 480 A, and 2400 A, respectively. - Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and is*R*_{4}2.08 A, 3.34 A, 0.833 A, and 4.17 A, respectively. - The same amount of current, 0.096 A, flows through all of the resistors.

#### 19.3 Parallel Circuits

- The appliances are connected in parallel to provide different voltage differences across each appliance.
- The appliances are connected in parallel to provide the same voltage difference across each appliance.
- The appliances are connected in series to provide the same voltage difference across each appliance.
- The appliances are connected in series to provide different voltage differences across each appliance.

#### 19.4 Electric Power

- No, the power dissipated remain same.
- Yes, the power dissipated increases.
- Yes, the power dissipated decreases.

- Batteries are connected in series for higher voltage and power output.
- Batteries are connected in series for lower voltage and power output.
- Batteries are connected in series so that power output is a much lower for the same amount of voltage.
- Batteries are connected in series to reduce the overall loss of energy from the circuit.