4 Series & parallel

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

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 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

A security light with the following all connected in series: a 5 Ω resistor, a 2 Ω lamp and an LDR which currently has 2 Ω of resistance would have a total resitance of 

• 9 Ω

• 7 Ω

• 2 Ω

• 1 Ω

• A

• B

• C

• D

What is the relationship between the readings on Ammeters A1, A2 and A3?

• A1 = A2 = A3

• A1 = A2 - A3

• A3 = A1 + A2

• A3 = A1 - A2

The current in the cell is 10 A as shown.

What is the current in the 2.0 Ω resistor?

• 0.35A

• 2.86A

• 3.50A

• 7.14A

Three resistors connected in parallel have individual values of 4.0, 6.0 and 10.0 ohm, respectively. If this combination is connected in series with a 12-V battery and a 2.0-ohm resistor, what is the current in the 10-ohm resistor?

• 0.59 A

• 1.0 A

• 11 A

• 16 A

Three resistors connected in parallel each carry currents labeled I₁, I₂ and I₃. Which of the following expresses the value of the total current I_T in the combined system?

• I_T = I₁ + I₂ + I₃

• I_T = (1/I₁ + 1/I₂ + 1/I₃)

• I_T = I₁ = I₂ = I₃

• I_T = (1/I₁ + 1/I₂ + 1/I₃)^-1

A 12 V circuit is connected to 2 lamps in parallel. If the total resistance in the circuit is 10 Ω, each lamp will receive a 

• 12 V potential difference carried by 0.6 A of current. 
• 12 V potential difference carried by 1.2 A of current. 
• 6 V potential difference carried by 0.6 A of current. 
• 6 V potential difference carried by 1.2 A of current.