PhysicsHelp.co.uk

Printable Physics practice

Six original questions. Worked answers start on a separate page.

· Forces, energy and momentum PDF · DC circuits and electrical energy PDF · Waves, phase and interference PDF · GCSE density and measurement PDF · GCSE heating and changes of state PDF · GCSE Hooke’s law and elastic energy PDF · GCSE practical calculations: mixed review PDF

Each set number reproduces the same questions. For classroom display or interactive checking, open a question’s practice link.

Treat the given values as exact unless an uncertainty is stated.

DC circuits and electrical energy

Set 42 · Original PhysicsHelp questions · Selected AQA 7408 / OCR A H556 skills

Question 1

Resistors of 70 Ω and 60 Ω are connected in series. Find the total resistance. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

12 V70 Ω60 Ω
Ideal 12 V supply. 70 Ω and 60 Ω resistors in series.

dc-circuits / series / v1.0.0 / seed 42 · Check interactively

Question 2

Resistors of 60 Ω and 70 Ω are connected in parallel. Find the total resistance. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

7 V60 Ω70 Ω
Ideal 7 V supply. 60 Ω and 70 Ω resistors in parallel.

dc-circuits / parallel / v1.0.0 / seed 104771 · Check interactively

Question 3

A 20 Ω resistor is in series with a parallel pair of 50 Ω and 100 Ω. An ideal 8 V supply is connected across the complete combination. Find the supply current. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

8 V20 Ω50 Ω100 Ω
Ideal 8 V supply. 50 Ω and 100 Ω resistors in parallel, with 20 Ω in series with the pair.

dc-circuits / mixed-current / v1.0.0 / seed 209500 · Check interactively

Question 4

A 60 Ω resistor and a 30 Ω resistor are in parallel across an ideal 11 V supply. Find current through the 60 Ω branch. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

11 V60 Ω30 Ω
Ideal 11 V supply. 60 Ω and 30 Ω resistors in parallel.

dc-circuits / branch-current / v1.0.0 / seed 314229 · Check interactively

Question 5

A steady current of 0.3 A flows for 9 min. Find the charge passing a point in the circuit. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

dc-circuits / charge / v1.0.0 / seed 418958 · Check interactively

Question 6

A 90 Ω resistor has 8 V across it. Find its electrical power dissipation. Give your answer to 3 significant figures.

Ideal DC supply, wires and meters. Resistors have constant resistance; heating does not change their values.

dc-circuits / resistor-power / v1.0.0 / seed 523687 · Check interactively

Worked answers — DC circuits and electrical energy

Set 42. Keep intermediate values unrounded. The stated practice checks accept values rounding to 3 significant figures.

Question 1

  1. R_total = 70 + 60 Ω.
  2. Answer: 130 Ω (3 significant figures).

Question 2

  1. R_total = (60 × 70)/(60 + 70) Ω.
  2. Answer: 32.3 Ω (3 significant figures).

Question 3

  1. R_parallel = (50 × 100)/(50+100) Ω.
  2. I = 8/[20 + (50 × 100)/(50+100)] A.
  3. Answer: 0.150 A (3 significant figures).

Question 4

  1. I_1 = 11/60 A.
  2. Answer: 0.183 A (3 significant figures).

Question 5

  1. t = 9 × 60 s.
  2. Q = 0.3 × 540 C.
  3. Answer: 162 C (3 significant figures).

Question 6

  1. P = 8²/90 W.
  2. Answer: 0.711 W (3 significant figures).