Chapter Review

Sections

Chapter Review

Concept Items

19.1 Ohm's Law

You connect a resistor across a battery. In which direction do the electrons flow?

The electrons flow from the negative terminal of the battery to the positive terminal of the battery.
The electrons flow from the positive terminal of the battery to the negative terminal of the battery.

How does current depend on resistance in Ohm’s law?

Current is directly proportional to the resistance.
Current is inversely proportional to the resistance.
Current is proportional to the square of the resistance.
Current is inversely proportional to the square of the resistance.

In the context of electricity, what is resistance?

Resistance is the property of materials to resist the passage of voltage.
Resistance is the property of materials to resist the passage of electric current.
Resistance is the property of materials to increase the passage of voltage.
Resistance is the property of materials to increase the passage of electric current.

What is the mathematical formula for Ohm’s law?

$V = I^{2} R$
$V = \frac{R}{I}$
$V = \frac{I}{R}$
$V = I R$

An accelerator accelerates He nuclei (change = 2e) to a speed of v = 2 × 10⁶ m/s. What is the current if the linear density of He nuclei is λ = 108 m^–1?

I = 9.6 × 10^–5 A
I = 3.2 × 10^–5 A
I = 12.8 × 10^–5 A
I = 6.4 × 10^–5 A

How can you verify whether a certain material is ohmic?

Make a resistor from this material and measure the current going through this resistor for several different voltages. If the current is proportional to the voltage, then the material is ohmic.
Make a resistor from this material and measure the current going through this resistor for several different voltages. If the current is inversely proportional to the voltage, then the material is ohmic.
Make a resistor from this material and measure the current going through this resistor for several different voltages. If the current is proportional to the square of the voltage, then the material is ohmic.
Make a resistor from this material and measure the current going through this resistor for several different voltages. If the current is inversely proportional to the square of the voltage, then the material is ohmic.

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.

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.

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

A battery of unknown voltage

V_{1}

is attached across a resistor

R_{1}

. You add a second battery with

V_{2} = 9.0 V

in series with

V_{1}

so that the voltage across

R_{1}

is now

V_{1} + V_{2}

and measure

0.3 A

of current through resistor

R_{1}

. You add a third battery with

V_{3} = 9.0 V

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

R_{3}

V_{1} + V_{2} + V_{3}

and measure

0.4 A

of current through

R_{1}

. What is the resistance of

R_{1}

$23.25 Ω$
$21.75 Ω$
$31.33 Ω$
$13.0 Ω$

19.2 Series Circuits

10.

In which circuit are all the resistors connected in series?

11. What is the voltage and current through the capacitor in the circuit below a long time after the switch is closed?

The figure shows a circuit with an open switch with one end connected to a capacitor. The other end of the capacitor is connected to the negative terminal of a 10-volt voltage source. The positive terminal of the voltage source is connected to the other end of the open switch. The connection between the capacitor and voltage source is also connected to the ground.

Figure 19.26

0 V, 0 A
0 V, 10 A
10 V, 0 A
10 V, 10 A

19.3 Parallel Circuits

12.

If you remove resistance from a circuit, does the total resistance of the circuit always decrease? Explain.

No, because for parallel combination of resistors, the resistance through the remaining circuit increases.
Yes, because for parallel combination of resistors, the resistance through the remaining circuit increases.

13.

Explain why the equivalent resistance of a parallel combination of resistors is always less than the smallest of the parallel resistors.

Adding resistors in parallel gives the current a shorter path through which it can flow hence decreases the overall resistance.
Adding resistors in parallel gives the current another path through which it can flow hence decreases the overall resistance.
Adding resistors in parallel reduce the number of paths through which the current can flow hence decreases the overall resistance.
Adding resistors in parallel gives the current longer path through which it can flow hence decreases the overall resistance.

19.4 Electric Power

14.

To draw the most power from a battery, should you connect a small or a large resistance across its terminals? Explain.

Small resistance, because smaller resistance will lead to the largest power
Large resistance, because smaller resistance will lead to the largest power

15.

If you double the current through a resistor, by what factor does the power dissipated by the resistor change?

Power increases by a factor of two.
Power increases by a factor of four.
Power increases by a factor of eight.
Power increases by a factor of 16.