### 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?

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

Through which branch in the circuit below does the most current flow?

- 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.

What current flows through the $75\text{-}\mathrm{\Omega}$ resistor in the circuit below?

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

What is the equivalent resistance for the circuit below if $\text{V}=9.0\phantom{\rule{thinmathspace}{0ex}}\text{V}$ and $I=0.25\phantom{\rule{thinmathspace}{0ex}}\text{A}$?

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

### 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.

In the circuit below, through which resistor(s) does the most current flow? Through which does the least flow? Explain.

- 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.