At a junction, 5.0 A flows in. 2.0 A flows out along one wire and 1.5 A along another. What current flows out along the third wire?
Answer and explanation
Correct answer: B. 1.5 amperes
- Step 1: Kirchhoff's first law: current in current out. Step 2. , so A. Answer: 1.5 amperes. Why not the others: 3.5 A ignores the 2.0 A branch; 3.0 A ignores the 1.5 A branch; 8.5 A adds all currents.
Practise more Electricity.
Free questions with an explanation for every one, and full timed A-Level UK (AQA, Edexcel, OCR) mock tests.
More Electricity questions
- A copper wire is 2.0 m long with cross-sectional area 0.50 mm2. The resistivity of copper is 1.7 x 10^-8 ohm m. What is its resistance?
- A cell has emf 12.0 V. When it supplies 2.0 A the terminal pd is 11.2 V. What is its internal resistance?
- A 9.0 V supply is connected across a 2.0 kilohm resistor in series with a 1.0 kilohm resistor. What is the pd across the 1.0 kilohm resistor…
- A 6.0 ohm and a 12 ohm resistor are in parallel, and this combination is in series with a 3.0 ohm resistor. What is the total resistance?
- A kettle is rated 2.3 kW at 230 V. What is the resistance of its heating element?
- What happens to the resistance of an NTC thermistor as its temperature increases?