Current, Voltage and Resistance

A 12 V battery is connected to a resistor of resistance $100\ \Omega$.

How much charge passes through the resistor in 30 minutes?

Options

A   3.6 C
B   220 C
C   250 C
D   $15\,000\ \text{C}$

A circuit consists of a resistor connected between the positive terminal and the negative terminal of a power supply.

Which row describes the direction of conventional current and the direction of flow of free electrons in the resistor?

Options

The graph shows how the resistance of a thermistor varies with temperature.

The thermistor is at a temperature of $10\,^\circ\text{C}$ and is connected in series with a fixed resistor of resistance $20\ \Omega$.

What is the combined resistance of both components?

Options

A   $16\ \Omega$
B   $20\ \Omega$
C   $80\ \Omega$
D   $100\ \Omega$

A quantity is defined as the work done by a source in moving unit charge around a complete circuit.

What is the quantity and what is its unit?

Options

Two resistors connected in series act as a potential divider as shown.

The resistors have resistances $R_1$ and $R_2$ and the potential differences across them are $V_1$ and $V_2$ respectively.

Which expression is equal to $\frac{V_1}{V_2}$?

Options

A   $\frac{R_1}{R_2}$
B   $\frac{R_2}{R_1}$
C   $\left(\frac{R_1}{R_2}\right)^2$
D   $\left(\frac{R_2}{R_1}\right)^2$

The diagram shows a lightning strike.

Charge flows between the cloud and objects on the ground.

During the lightning strike, there is a current of $2.8 \times 10^4\ \text{A}$ between the cloud and the house for $52\ \text{ms}$.

How much charge flows during the lightning strike?

Options

A   $1500\ \text{C}$
B   $15\,000\ \text{C}$
C   $24\,000\ \text{C}$
D   $54\,000\ \text{C}$

A cardboard tube has two wires, P and Q, connected to its ends. Inside the tube, wire P and wire Q are connected to two resistors.

The potential difference (p.d.) between wire P and wire Q is $9.0\ \text{V}$ and the current in the wires is $0.75\ \text{A}$.

Which combination of resistors is inside the tube?

Options

A   a $0.75\ \Omega$ resistor and a $6.0\ \Omega$ resistor in parallel
B   a $0.75\ \Omega$ resistor and a $6.0\ \Omega$ resistor in series
C   a $20\ \Omega$ resistor and a $30\ \Omega$ resistor in parallel
D   a $20\ \Omega$ resistor and a $30\ \Omega$ resistor in series

A resistor of resistance $R$ is connected to a variable resistor, a voltmeter and a power supply of electromotive force (e.m.f.) $E$.

The resistance of the variable resistor increases from $0$ to $2R$.

What happens to the reading on the voltmeter?

Options

A   It increases from $0$ to $\frac{1}{3}E$.
B   It increases from $0$ to $\frac{1}{2}E$.
C   It increases from $0$ to $\frac{2}{3}E$.
D   It increases from $0$ to $E$.

Which equation is correct for potential difference (p.d.)?

Options

A   $\text{p.d.} = \text{voltage} \times \text{current}$
B   $\text{p.d.} = \frac{\text{energy}}{\text{time}}$
C   $\text{p.d.} = \frac{\text{work done}}{\text{charge}}$
D   $\text{p.d.} = \frac{\text{current}}{\text{resistance}}$

Which quantity is defined as the electrical work done by a source in moving a unit charge around a complete circuit?

Options

A   power
B   potential difference
C   electromotive force
D   energy