Electricity

Two cylindrical conductors, X and Y, are made from the same material. The conductors have equal lengths, but Y has a smaller diameter than X.
X and Y are connected in series to a cell.
Which row compares the number of charge carriers per unit time passing through X and through Y and compares the average drift speed of the charge carriers in X and in Y?

Options

A copper wire is $6.4\text{ m}$ long and has a resistance of $0.92\,\Omega$.
The resistivity of copper is $1.8 \times 10^{-8}\,\Omega\text{ m}$.
What is the diameter of the wire?

Options

A   $5.7 \times 10^{-5}\text{ m}$
B   $1.0 \times 10^{-4}\text{ m}$
C   $4.0 \times 10^{-4}\text{ m}$
D   $7.1 \times 10^{-4}\text{ m}$

A thermistor is connected to a cell with negligible internal resistance.

Which graph shows the variation with temperature of power, $P$, dissipated in the thermistor?

Options

A metal electrical conductor has a resistance of $5.6\text{ k}\Omega$. A potential difference (p.d.) of $9.0\text{ V}$ is applied across its ends.
How many electrons pass a point in the conductor in one minute?

Options

A   $6.0 \times 10^{20}$
B   $1.0 \times 10^{19}$
C   $6.0 \times 10^{17}$
D   $1.0 \times 10^{16}$

The diagram shows a junction in a circuit where three wires, P, Q and R, meet. The currents in P and Q are $1\text{ A}$ and $3\text{ A}$ respectively, in the directions shown.

How much charge passes a given point in wire R in a time of $5\text{ s}$?

Options

A   $0.4\text{ C}$
B   $2\text{ C}$
C   $10\text{ C}$
D   $20\text{ C}$

Which expression gives the definition of resistance?

Options

A   current divided by potential difference
B   current multiplied by potential difference
C   potential difference divided by current
D   resistivity multiplied by length

The graph shows the $I$–$V$ characteristic of an electrical component.

What is the component?

Options

A   a filament lamp
B   a metallic conductor at constant temperature
C   a resistor
D   a semiconductor diode

The diagram shows six identical resistors connected in a circuit.

In which branch of the circuit is the most power dissipated?

Options

A   PQ
B   QR
C   RS
D   SP

The diagram shows a circuit containing a thermistor, a fixed resistor and a battery.

The graph shows the $I$–$V$ characteristics of both components.

The battery has an e.m.f. of $12\text{ V}$ and negligible internal resistance.

What is the current in the fixed resistor?

Options

A   $0.36\text{ mA}$
B   $0.40\text{ mA}$
C   $0.48\text{ mA}$
D   $0.80\text{ mA}$

A wire is made from a metal of constant resistivity. There is a constant current in the wire.

Which statement about the potential difference across the wire is correct?

Options

A   It is directly proportional to the length of the wire.
B   It is inversely proportional to the length of the wire.
C   It is directly proportional to the diameter of the wire.
D   It is inversely proportional to the diameter of the wire.