Physics notes: Current and D.C. Circuits

1. If wire X has twice the resistance of wire Y and has a radius that is one third of wire Y’s radius, what is the ratio of the resistivity of wire X and wire Y?

2. A battery delivers 10 000 J of energy to a 20W rice cooker. How long will the cooker run before the battery dries up?

3. Bulbs A and B are connected in parallel. Bulb A is in series with a thermistor and bulb B is in series with a light dependant resistor. What happens if the temperature suddenly increases and the lights go off?

4. What is a rheostat used for?

5. A parallel circuit has 10 branches with a resistor in each branch. A new branch with a 2Ω resistor is added. What happens to the voltage of the entire circuit?

6. A single bulb in a series circuit with a resistance of 3Ω has a rating of 6V. What is the charge passing through it in 1 second?Substance X has a resistivity of 1.23. It is used to make a wire that is 30cm long with a diameter of 3mm. What is the resistance of the wire?

7. 2 bulbs with negligible internal resistance are connected in parallel with a dry cell that has an e.m.f. of 12V. What is the current passing through each bulb if the effective resistance of the circuit due to the wires is R?

8. If the efficiency of a bulb rated 240V, 75W is 75%, what is the work done by it in converting electrical energy to heat and light energy when it is used for 10 minutes?

9. A bulb has a rating of 6V. What does this mean?

10. A single bulb in a series circuit with a resistance of 3Ω has a rating of 6V. What is the charge passing through it in 30 seconds?

1. If wire X has twice the resistance of wire Y and has a radius that is one third of wire Y’s radius, what is the ratio of the resistivity of wire X and wire Y?

2. A battery delivers 10 000 J of energy to a 20W rice cooker. How long will the cooker run before the battery dries up?

3. Bulbs A and B are connected in parallel. Bulb A is in series with a thermistor and bulb B is in series with a light dependant resistor. What happens if the temperature suddenly increases and the lights go off?

4. What is a rheostat used for?

5. A parallel circuit has 10 branches with a resistor in each branch. A new branch with a 2Ω resistor is added. What happens to the voltage of the entire circuit?

6. A single bulb in a series circuit with a resistance of 3Ω has a rating of 6V. What is the charge passing through it in 1 second?Substance X has a resistivity of 1.23. It is used to make a wire that is 30cm long with a diameter of 3mm. What is the resistance of the wire?

7. 2 bulbs with negligible internal resistance are connected in parallel with a dry cell that has an e.m.f. of 12V. What is the current passing through each bulb if the effective resistance of the circuit due to the wires is R?

8. If the efficiency of a bulb rated 240V, 75W is 75%, what is the work done by it in converting electrical energy to heat and light energy when it is used for 10 minutes?

9. A bulb has a rating of 6V. What does this mean?

10. A single bulb in a series circuit with a resistance of 3Ω has a rating of 6V. What is the charge passing through it in 30 seconds?