Question 1

A real battery is modeled as an ideal voltage source $$V in $$series with an internal resistance $$r. If a $$load resistor $$R_L is $$connected across the battery, what is the voltage $$V_L$$ across the load resistor?

Accepted Answer

$$V_L = V \frac{R_L}{R_L + r}$$

Question 2

In the circuit shown, a battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to a resistor $$R. $$What is the current $$I in $$the circuit?

Accepted Answer

$$I = \frac{\mathcal{E}}{R + r}$$

Question 3

A voltmeter should always be connected in which way in a circuit?

Accepted Answer

In parallel with the component

Question 4

A $$1.5\,\mathrm{V}$$ battery is connected to a $$20\,\Omega$$ resistor. What is the power dissipated in the resistor?

Accepted Answer

$$0.113\,\mathrm{W}$$

Question 5

Which equation correctly expresses the voltage across a resistor $$R$$ when a current $$I$$ flows from $$a to$$ $$b$$?

Accepted Answer

$$V_b = V_a - IR$$

Question 6

A $$9.0\,\mathrm{V}$$ battery supplies $$360\,\mathrm{mA} to a $$resistor. What is the power dissipated in the resistor?

Accepted Answer

$$3.24\,\mathrm{W}$$

Question 7

If the internal resistance $$r of a $$battery increases significantly, what happens to the voltage across the load $$R_L$$?

Accepted Answer

It decreases

Question 8

In a circuit with two batteries and three resistors as shown, which law would you use to write equations for the currents at a junction?

Accepted Answer

Kirchhoff's Junction Rule

Question 9

A real battery has emf $$V$$ and internal resistance $$r. If $$the load resistance $$R_L is $$much larger than $$r$$, what is the approximate voltage across the load?

Accepted Answer

$$V_L \approx V$$

Question 10

Which of the following best describes why a battery 'dies' over time, even though the chemical reaction can still produce a potential difference?

Accepted Answer

The internal resistance $$r$$ increases, reducing the voltage available to the load

Question 11

Given a circuit with a $$12\,\mathrm{V}$$ battery, $$25\,\Omega$$ and $$50\,\Omega$$ resistors in series, what is the current through the circuit?

Accepted Answer

$$0.11\,\mathrm{A}$$

Question 12

If a voltmeter reads $$8.3\,\mathrm{V}$$ across a battery and the current is $$0.11\,\mathrm{A}$$, what is the total resistance in the circuit?

Accepted Answer

$$75.45\,\Omega$$

Question 13

A digital multimeter is set to measure voltage. How should it be connected to a circuit to measure the voltage across a resistor?

Accepted Answer

In parallel with the resistor

Question 14

Which equation correctly gives the power dissipated in a resistor $$R$$ with voltage $$V$$ across it?

Accepted Answer

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

Question 15

In a circuit, if you reverse the assumed direction of current and get a negative value for current, what does this mean?

Accepted Answer

The current flows in the opposite direction to your assumption

Question 16

If a resistor $$R is $$connected to an ideal battery of voltage $$V$$, what is the current through the resistor?

Accepted Answer

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

Question 17

Which of the following is true for the voltage across a resistor when the current flows from $$b to$$ $$a ($$opposite to the direction shown in the diagram)?

Accepted Answer

$$V_b = V_a + IR$$

Question 18

A battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to a load $$R_L. If$$ $$r$$ increases over time, what happens to the current in the circuit?

Accepted Answer

It decreases

Question 19

Which of the following best describes the difference between an ideal and a real battery?

Accepted Answer

A real battery has internal resistance, while an ideal battery does not

DC Circuits, Batteries, and RC Circuits: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards