Question 1

A battery has an e.m.f. $$E$$ and internal resistance $$r. It is $$connected to an external resistor $$R. $$Which equation correctly relates the terminal potential difference $$V to $$the current $$I in $$the circuit?

Accepted Answer

$$V = E - Ir$$

Question 2

A 5.0 V battery with an internal resistance of $$2.0\ \Omega is $$connected to an $$8.0\ \Omega$$ resistor. What is the current in the circuit?

Accepted Answer

$$0.5\ \mathrm{A}$$

Question 3

Four identical cells, each with e.m.f. $$1.5\ \mathrm{V}$$ and internal resistance $$0.10\ \Omega$$, are connected in series to a $$2.0\ \Omega$$ lamp. What is the current through the lamp?

Accepted Answer

$$2.73\ \mathrm{A}$$

Question 4

A high-resistance voltmeter reads $$3.0\ \mathrm{V}$$ across a battery. When a $$10\ \Omega$$ resistor is connected across the battery, the reading drops to $$2.8\ \mathrm{V}. $$What is the internal resistance of the battery?

Accepted Answer

$$0.71\ \Omega$$

Question 5

A car battery has an e.m.f. of $$12\ \mathrm{V}$$ and internal resistance $$0.04\ \Omega. If $$the starter motor draws $$100\ \mathrm{A}$$, what is the terminal p.d. of the battery while the starter is operating?

Accepted Answer

$$8.0\ \mathrm{V}$$

Question 6

Each headlamp in a car is rated at $$12\ \mathrm{V}, 36\ \mathrm{W}. $$What is the resistance of one headlamp?

Accepted Answer

$$4.0\ \Omega$$

Question 7

If the headlamp resistance remains constant, what will be the power output of each headlamp when the battery terminal p.d. drops to $$8.0\ \mathrm{V}$$ due to the starter motor?

Accepted Answer

$$16\ \mathrm{W}$$

Question 8

In a potential divider circuit with $$R_1 = 10$$\ \Omega$$ and R_2$ variable from 0$ to 40$$\ \Omega$$, and a supply voltage of 10$$\ \mathrm{V}$$, what is the maximum possible output voltage V$$_{out}$$?

Accepted Answer

$$8.0\ \mathrm{V}$$

Question 9

Which equation gives the output voltage $$V_{out}$$ for a potential divider with resistors $$R_1$$ and $$R_2$$ connected in series to a supply voltage $$V_{in}$$?

Accepted Answer

$$V_{out} = \frac{R_2$}{R_1$ + R_2$} V_{in}$$

Question 10

A potentiometer wire of length $$AB is $$used to compare the e.m.f. $$E_X of a $$cell with a standard cell of e.m.f. $$E_0. If $$the balance point is at $$AY$$, which equation gives $$E_X$$?

Accepted Answer

$$E_X = \frac{AY}{AB} E_0$

Question 11

In a potentiometer experiment, the balance points for two cells $$X$$ and $$Y$$ are at $$AC$$ and $$AD$$ respectively. Which equation correctly relates their e.m.f.s?

Accepted Answer

$$\frac{E_X}{E_Y} = \frac{AC}{AD}$$

Question 12

Why is a potentiometer preferred over a voltmeter for measuring e.m.f.?

Accepted Answer

Because it does not draw current from the cell being measured

Question 13

A battery with e.m.f. $$E$$ and internal resistance $$r is $$connected to a load resistor $$R. If$$ $$R is $$increased, what happens to the terminal p.d. $$V$$?

Accepted Answer

It increases

Question 14

In a circuit, the term 'lost volts' refers to:

Accepted Answer

The potential difference across the internal resistance of the source

Question 15

A potential divider is used to supply a variable voltage to a device. If $$R_1 = 10$$\ \Omega$$ and R_2$ is varied from 0$ to 40$$\ \Omega$$ with V$$_{in} = 10\ \mathrm{V}$$, what is the minimum value of V$$_{out}$$?

Accepted Answer

$$0\ \mathrm{V}$$

Question 16

In a potentiometer experiment, why must the galvanometer show zero deflection at the balance point?

Accepted Answer

Because the potential difference across the wire equals the e.m.f. being measured

Question 17

If two resistors $$R_1$$ and $$R_2$$ are connected in series to a voltage $$V_{in}$$, and $$V_{out} is $$measured across $$R_2$$, which of the following will increase $$V_{out}$$?

Accepted Answer

Increasing $$R_2$$

Question 18

A battery has an e.m.f. of $$6.0\ \mathrm{V}$$ and an internal resistance of $$1.0\ \Omega. If it is $$connected to a $$5.0\ \Omega$$ resistor, what is the power dissipated in the internal resistance?

Accepted Answer

$$1.0\ \mathrm{W}$$

Practical Circuits Unit Overview

Study Guide - Practice Questions

Study Guide - Flashcards