Kirchhoff's laws

An electrical junction has three wires A, B and C connected to it. Wire A carries 4.2 A going in, wire B carries 2.6 A going out. What does wire C carry?

• 1.6 A going in

• 1.6 A going out

• 6.8 A going in

• 6.8 A going out

A closed loop contains 2 batteries and two resistors. The batteries produce 3 V and 4.5 V respectively. If the voltage across one resistor is 1 V what could the voltage across the second resistor be? (Hint: polarity)

• 1 V

• 7.5 V

• 0.5 V

• 1.5 V

An electrical junction has four wires A, B, C and D connected to it. Wire A carries 7A going in, wire B carries 5 A going out and wire C carries 2 A going in. What does wire D carry?

• 10 A going out

• 5 A going out

• 4 A going in

• 4 A going out

A closed loop contains 3 batteries and two resistors. The batteries produce 6.5 V, 3.2 V and 2.8 V respectively. If the voltage across one resistor is 5.1 V what could the voltage across the second resistor be? (Hint: polarity)

• 1.8 V

• 7.2 V

• 1.2 V

• 12.3 V

Current is shared between two resistors of 3 Ω and 6 Ω, if the current in the 6 Ω is 12 A what is the total incoming current?

• 24 A

• 36 A

• 18 A

• 72 A

A potential divider contains three resistors of 4 Ω, 7 Ω and

9 Ω. If the voltage across the 7 Ω is 21 V, what is the supply voltage?

• 21 V

• 63 V

• 33 V

• 60 V

Analysis of a circuit produces two loop equations:

10x + 30y = 7 and 40x - 20y = 0

What are the currents x and y?

• x = 50 and y = 10

• x = 0.2 and y = 0.1

• x = 0.01 and y = 0.02

• y = 0.2 and x = 0.1

Select the correct statement:

• The current in parallel resistors is always equal.

• The sum of the sources of EMF and volt-drops in a closed loop is zero.

• The sum of the currents in a closed loop is zero.

• The sum of the voltages at a node is zero.