Paul Peter Urone; Roger Hinrichs

Problems

19.1 Ohm's law

20.

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

The required voltage is 1 × 10⁻³ V.
The required voltage is 10 V.
The required voltage is 1,000 V.
The required voltage is 10,000 V.

21.

Resistors typically obey Ohm’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 Ohm’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.

$V = a I$
$V = a I + b$
$V = a I + b I^{2}$
$V = a I + b I^{2} + c$

22 .

A battery of unknown voltage

V_1

is attached across a resistor

R_1

. You add a second battery with

V_2 = 9.0\,\text{V}

in series with

V_1

so that the voltage across

R_1

is now

V_1 + V_2

and measure

0.3\,\text{A}

of current through resistor

R_1

. You add a third battery with

V_3 = 9.0\,\text{V}

in series with the first two batteries so that the voltage across

R_1

is

V_1 + V_2 + V_3

and measure

0.4\,\text{A}

of current through

R_1

. What is the resistance of

R_1

?

$23.25\,\Omega$
$21.75\,\Omega$
$31.33\,\Omega$
$90\,\Omega$

19.2 Series Circuits

23.

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

12 V
24 V
36 V
48 V

24.

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

The figure shows a rectangular circuit with a battery and two resistors connected in series. The battery is located on the left-hand segment of the circuit, a 30-ohm resistor is located on the upper segment, and a 50-ohm resistor is located on the right-hand segment of the circuit.

4.5V
7.5V
12V
18V

19.3 Parallel Circuits

25.

What is the equivalent resistance of this circuit?

The figure shows a circuit with three resistors. The first resistor is horizontal and labeled 150 ohms. The left end of the first resistor is connected to a second resistor of 250 ohms. The other end of the second resistor is connected to a third resistor of 50 ohms, which in turn is connected to the right end of the first resistor.

The equivalent resistance of the circuit is 32.7 Ω.
The equivalent resistance of the circuit is 100 Ω.
The equivalent resistance of the circuit is 327 Ω.
The equivalent resistance of the circuit is 450 Ω.

26.

What is the equivalent resistance of the circuit shown below?

A circuit contains six resistors that are arranged in an outer circuit enclosing an inner circuit. The outer circuit has a 100-ohm horizontal resistor. Left end of the resistor is connected to a second resistor of 50 ohms. The other end of the second resistor is connected to a third resistor of 50 ohms, which in turn is connected to the right end of the first resistor. The inner circuit is identical to the outer circuit, and the left and right ends of both the circuits are connected. In addition, there is a line connecting the points between the two 50-ohm resistors of each circuit.

The equivalent resistance is 25 Ω.
The equivalent resistance is 50 Ω.
The equivalent resistance is 75 Ω.
The equivalent resistance is 100 Ω.

19.4 Electric Power

27.

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.

28.

Warming 1 g of water requires 4.18 J of energy per °C. How long would it take to warm 1 L of water from 20 to 40 °C if you immerse in the water a 1-kW resistor connected across a 9.0-V battery?

10 min
20 min
30 min
40 min