Electricity in the Home and Electromagnetism

What is another way to calculate the cost of electricity used?

• Cost = Power (kW) x Time (h) x Cost of 1 kWh

• Cost = Voltage x Current x Cost of 1 kWh

• Cost = Resistance x Time x Cost of 1 kWh

• Cost = Power (W) x Time (s) x Cost of 1 kWh

Answer explanation

The correct formula to calculate electricity cost is Cost = Power (kW) x Time (h) x Cost of 1 kWh. This accounts for the power used over time, multiplied by the cost per kilowatt-hour.

What is the result when the switches are in the positions shown in the diagram?

• The lamp would be off

• The lamp would be on

• The circuit would be complete

• The current would increase

Answer explanation

The lamp would be off because the switches are positioned in a way that breaks the circuit, preventing current from flowing to the lamp.

What type of switch is used beside a door to control a light?

• One-way switch

• Two-way switch

• Three-way switch

• Dimmer switch

Answer explanation

A one-way switch is typically used beside a door to control a light, allowing it to be turned on or off from a single location. Other switches like two-way or three-way are used for multiple control points.

What material are the wires in a three-pin plug coated with?

• Rubber

• Plastic

• Metal

• Wood

Answer explanation

The wires in a three-pin plug are coated with plastic to provide insulation and safety. Plastic is a non-conductive material that helps prevent electrical shocks, making it the correct choice over rubber, metal, or wood.

What is the function of the earth wire?

• To conduct electricity to the device

• To provide a path for current to flow to the ground

• To increase voltage

• To convert AC to DC

Answer explanation

The earth wire provides a safe path for excess current to flow to the ground, preventing electric shock and equipment damage. This is crucial for safety, making it the correct choice.

Where is the blue wire positioned in a plug?

• Top

• Bottom Left

• Bottom Right

• Center

Answer explanation

In a standard plug, the blue wire is typically positioned in the bottom left slot. This is important for proper electrical connections, ensuring safety and functionality.

What color is the insulation of the neutral wire in a three-pin plug?

• Brown

• Blue

• Yellow and Green

• Red

Answer explanation

In a three-pin plug, the insulation of the neutral wire is colored blue. This is standardized in electrical wiring, where brown indicates live, blue indicates neutral, and yellow/green indicates earth.

What indicates the direction of current flow in an a.c. supply?

• The color of the wire

• The positive and negative values

• The length of the wire

• The thickness of the wire

Answer explanation

In an a.c. supply, the direction of current flow is indicated by the positive and negative values, which alternate over time. This is essential for understanding how alternating current operates.

What is the angle between the direction of the force and the magnetic field?

• 0°

• 45°

• 90°

• 180°

Answer explanation

The angle between the direction of the force and the magnetic field is 90°. This is because the force on a charged particle moving in a magnetic field is always perpendicular to both the velocity of the particle and the magnetic field.

What is the direction of the magnetic field in the worked example?

• From S to N

• From N to S

• From E to W

• From W to E

Answer explanation

The magnetic field direction is conventionally defined as going from the North (N) pole to the South (S) pole. Therefore, the correct answer is 'From N to S'.