Practical Electricity

There is an electric current of $1.5\ \text{A}$ in a $4.0\ \Omega$ resistor.

How much energy is transferred electrically to thermal energy in $1.0\ \text{minute}$?

Options

A   $6.0\ \text{J}$
B   $360\ \text{J}$
C   $540\ \text{J}$
D   $1440\ \text{J}$

A kettle of power $2.0\ \text{kW}$ is powered by the $230\ \text{V}$ mains supply.

What is the appropriate rating for the fuse in the circuit?

Options

A   $1\ \text{A}$
B   $5\ \text{A}$
C   $13\ \text{A}$
D   $20\ \text{A}$

A potential difference of $4.0\text{ V}$ produces a current of $3.0\text{ A}$ in a resistor.

How much energy is transferred to thermal energy during $10\text{ s}$?

Options

A   $12\text{ J}$
B   $30\text{ J}$
C   $40\text{ J}$
D   $120\text{ J}$

Which electrical appliance uses the heating effect of electricity?

Options

A   a cell phone (mobile phone)
B   a fan
C   a hairdryer
D   a lawnmower

How many kilowatt-hours of energy are used by a $1000\ \text{W}$ heater connected to a $230\ \text{V}$ supply for 30 minutes?

Options

A   $0.30\ \text{kWh}$
B   $0.50\ \text{kWh}$
C   $30\ \text{kWh}$
D   $120\ \text{kWh}$

Which safety precautions must be taken when wiring an electrical kettle that has a stainless-steel outer casing?

Options

A   It must be earthed and have a fuse in the live wire.
B   It must be earthed and have a fuse in the neutral wire.
C   It needs a fuse in the live wire but does not need to be earthed.
D   It needs a fuse in the neutral wire but does not need to be earthed.

What is the purpose of the earth wire in a plug connected to an appliance?

Options

A   to complete the circuit so that the appliance works
B   to conduct thermal energy so that the appliance does not get too hot
C   to prevent a person getting a shock
D   to protect the appliance from a current that is too large

The current in a home computer varies between $0.40\ \text{A}$ and $1.2\ \text{A}$ when the computer is connected to the mains supply.

What is the rating of the most suitable fuse to use to protect the computer?

Options

A   $0.5\ \text{A}$
B   $1.2\ \text{A}$
C   $1.5\ \text{A}$
D   $13\ \text{A}$

Three students each suggest a consequence of wiring lamps in parallel rather than in series.

student 1: If one lamp breaks, the other lamps stay lit.
student 2: The lamps can be switched on and off separately.
student 3: The p.d. across each lamp is equal to the p.d. across the supply.

Which students are correct?

Options

A   1, 2 and 3
B   1 and 2 only
C   1 and 3 only
D   2 and 3 only

The power consumption of a microwave oven is $1500\text{ W}$.

The cost of $1.0\text{ kWh}$ of electrical energy is 24 cents.

What is the cost of using the microwave oven for 10 minutes?

Options

A   6 cents
B   36 cents
C   60 cents
D   360 cents