Worked example
An ideal ohmic resistor has resistance 4 Ω and voltage 12 V across it. What current flows?
Answer & why
Answer: 3 A
I = V ÷ R = 12 ÷ 4 = 3 A.
Grade 11 · Science
Relate voltage, current and resistance
Use V = IR for a stated ideal ohmic component and keep amperes, volts and ohms distinct.
6 authored questions + worked example
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All questions
All 6 authored questions for this skill.
Question 1
An ideal resistor has 6 V across 6 Ω. What current flows?
- 3 A
- 2 A
- 4 A
- 1 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 1 A
I = 6 ÷ 6 = 1 A.
Question 2
An ideal resistor has 20 V across 5 Ω. What current flows?
- 2 A
- 4 A
- 3 A
- 1 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 4 A
I = 20 ÷ 5 = 4 A.
Question 3
An ideal resistor has 15 V across 3 Ω. What current flows?
- 2 A
- 5 A
- 1 A
- 3 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 5 A
I = 15 ÷ 3 = 5 A.
Question 4
An ideal resistor has 18 V across 3 Ω. What current flows?
- 1 A
- 2 A
- 3 A
- 6 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 6 A
I = 18 ÷ 3 = 6 A.
Question 5
An ideal ohmic resistor has resistance 4 Ω and voltage 12 V across it. What current flows?
- 1 A
- 2 A
- 4 A
- 3 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 3 A
I = V ÷ R = 12 ÷ 4 = 3 A.
Question 6
An ideal resistor has 10 V across 5 Ω. What current flows?
- 1 A
- 2 A
- 4 A
- 3 A
A hint
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Answer & why
Answer: 2 A
I = 10 ÷ 5 = 2 A.