20 multiple choice A level electricity Q

In the circuit shown, the cell has an emf of 12 V and an internal resistance which is not negligible. When the resistance of the variable resistor is 10 Ω the voltmeter reads 10 V and the ammeter reads 1.0 A. The resistance of the variable resistor is changed to 5 Ω. What is the new reading on the ammeter?

• 1.4 A
• 1.7 A
• 2.0 A
• 2.4 A

Two identical batteries each of emf 1.5 V and internal resistance 1.6 Ω are connected in parallel. A 2.4 Ω resistor is connected in parallel with this combination. What is the current in the 2.4 Ω resistor?

• 0.38 A
• 0.47 A
• 0.75 A
• 0.94 A

A resistor with resistance R is made from metal wire of resistivity ρ. The length of the wire is L.What is the diameter of the wire?

• A
• B
• C
• D

In the circuit below, the voltmeter reading is zero. When the temperature of the thermistor T is increased, the voltmeter reading changes. Which change to the circuit will restore the voltmeter to zero?

• a reduction in the emf of the cell
• a reduction in the resistance of P
• an increase in the resistance of Q
• a reduction in the resistance of R

Three identical cells, each of emf 1.5 V and internal resistance 6.0 Ω, are connected to resistor R. The resistance of R is 6.0 Ω. What is the current in R?

• 0.19 A
• 0.25 A
• 0.56 A
• 0.75 A

A power of 100 kW at a potential difference of 10 kV is transmitted to a load resistor through cables of total resistance 5.0 Ω. What is the power loss in the cables?

• 50 W
• 0.5 kW
• 100 kW
• 20 MW

The diagram shows a network of four 2 Ω resistors. The effective resistance, in Ω, between X and Y is

• 0.5
• 1.2
• 1.7
• 2.0

The diagram shows two wires, P and Q, of equal length, joined in series with a cell. A voltmeter is connected between the end of Q and a point X on the wires. The p.d. across the cell is V. Wire Q has twice the area of cross-section and twice the resistivity of wire P. The variation of the voltmeter reading as the point X is moved along the wires is best shown by(Total 1 mark)

• a
• b
• c
• d

Copper metal is a good conductor of electricity because copper atoms in copper metal

• have gained an extra or "free" electron
• are ionised so that both ions and "free" electrons can move
• have a negative charge because of the "free" electrons
• have lost an electron to form positive ions and "free" electrons

The 12 V battery in the circuit shown has negligible internal resistance. The diodes have 'ideal' characteristics. The current through the battery is approximately

• 0 A
• 0.10 A
• 0.20 A
• 0.40 A