Gr 10 Science test

The potential difference across a car headlamp is 12V. The current across the lamp is 2.5 A. The resistance of the lamp is?

• 30 Ohms

• 30 Newtons

• 4.8 Ohms

• 4.8 Newtons

The potential difference across a car headlamp is 12V. The current is 2.5 A. How much energy is transferred by the lamp in 1 hour?

• 1800 J

• 1800 W

• 108000 J

• 108000 W

A 100% efficient transformer has 60000 turns across the primary coil and 600 turns across the secondary coil. The output voltage of the transformer is 12V. A resistor is connected across the secondary transformer and dissipates 24 W of power. What is the current in the primary coil of the transformer?

• 0.0050 A

• 0.20A

• 5.0 A

• 20 A.

The diagram shows a circuit. Switch S is closed. Which lamp will light?

• Lamp 1 only

• Lamp 2 only

• Lamp 1 and 2

• Neither lamp 1 or 2

A circuit contains 4 ammeters and 3 resistors with different values, as seen in the diagram. Which ammeter will show the largest reading?

• A

• B

• C

• D

The current in a coil (solenoid) enters from the right and produces a magnetic field around it. If the magnitude of the of the potential difference across the coil is increased and its direction is reversed, what happens to the magnetic field?

• The magnetic field lines will become closer together and the right hand end becomes the South pole

• The magnetic field lines will become closer together and the right hand end remains the North pole

• The magnetic field lines will move further apart and the right hand end becomes the South pole

• The magnetic field lines will move further apart and the right hand end remains the North pole

A 3.0 Ω and a 4.0 Ω are connected in parallel. What is the total resistance of this combination?

• 0.14 Ω

• 0.58 Ω

• 1.7 Ω

• 7 Ω

A student sets up this circuit. What is the purpose of this circuit?

• To allow a lamp to be made brighter or dimmer as required.

• to amplify the sound of a voice.

• To light a lamp in the dark.

• To sound a bell when the temperature rises.

A bar magnet is placed inside a current carry coil. The diagram shows four different experiments. In which experiments is the magnet demagnetised?

• 1 and 2

• 1 and 3

• 2 and 4

• 3 and 4

Copper wire is available in fixed lengths but various diameters d. Each diameter has a different resistance R. Which relationship between R and d is correct?

• R is directly proportional to d.

• R is directly proportional to d2

• R is inversely proportional to d

• R is inversely proportional to d2