### Problems

#### 19.1 Ohm's law

What voltage is needed to make 6 C of charge traverse a 100-Î© resistor in 1 min?

- The required voltage is 1 Ã— 10
^{âˆ’3}V. - The required voltage is 10 V.
- The required voltage is 1,000 V.
- The required voltage is 10,000 V.

Resistors typically obey Ohmâ€™s law at low currents, but show deviations at higher currents because of heating. Suppose you were to conduct an experiment measuring the voltage, *V*, across a resistor as a function of current, *I*, including currents whose deviations from Ohmâ€™s law start to become apparent. For a data plot of *V* versus *I*, which of the following functions would be best to fit the data? Assume that *a, b*, and *c* are nonzero constants adjusted to fit the data.

- $$V=aI$$
- $$V=aI+b$$
- $$V=aI+b{I}^{2}$$
- $$V=aI+b{I}^{2}+c$$

- 23.25\,\Omega
- 21.75\,\Omega
- 31.33\,\Omega
- 90\,\Omega

#### 19.2 Series Circuits

What is the voltage drop across two 80-Î© resistors connected in series with 0.15 A flowing through them?

- 12 V
- 24 V
- 36 V
- 48 V

In this circuit, the voltage drop across the upper resistor is 4.5 V. What is the battery voltage?

- 4.5V
- 7.5V
- 12V
- 18V

#### 19.3 Parallel Circuits

What is the equivalent resistance of this circuit?

- The equivalent resistance of the circuit is 32.7 Î©.
- The equivalent resistance of the circuit is 100 Î©.
- The equivalent resistance of the circuit is 327 Î©.
- The equivalent resistance of the circuit is 450 Î©.

What is the equivalent resistance of the circuit shown below?

- The equivalent resistance is 25 Î©.
- The equivalent resistance is 50 Î©.
- The equivalent resistance is 75 Î©.
- The equivalent resistance is 100 Î©.

#### 19.4 Electric Power

When 12 V are applied across a resistor, it dissipates 120 W of power. What is the current through the resistor?

- The current is 1,440 A.
- The current is 10 A.
- The current is 0.1 A.
- The current is 0.01 A.

Warming 1 g of water requires 1 J of energy per . How long would it take to warm 1 L of water from 20 to 40 Â°C if you immerse in the water a 1-kW resistor connected across a 9.0-V batteries aligned in series?

- 10 min
- 20 min
- 30 min
- 40 min