Energy and Voltage in Circuits
4 marks · NormalA circuit contains a battery and two resistors, R1 and R2, connected in series. R1 = 4 Ω and R2 = 8 Ω. The battery supplies a voltage of 12 V.
Calculate the total resistance in the circuit.
Calculate the current in the circuit.
Calculate the voltage across R2.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 12 Ω
(b) 1.0 A
(c) 8 V
Common mistakes: Adding only one resistor; Using wrong formula for current; Not dividing voltage for resistor
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly adds resistances in series: R = R1 + R2.
M2 (b) · 1 mark · Uses V = I × R, rearranges to I = V / R.
A1 (b) · 1 mark · Correct value for current with total resistance from (a). (follow-through)
A2 (c) · 1 mark · Correct calculation of voltage across R2: V = I × R2. (follow-through)
Worked solution
a) Total resistance, R = R1 + R2 = 4 Ω + 8 Ω = 12 Ω
b) Current, I = V / R = 12 V / 12 Ω = 1.0 A
c) Voltage across R2: V = I × R2 = 1.0 A × 8 Ω = 8 V