Twenty Questions

Electricity 1

Twenty Questions

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

16 17 18 19 20

1. State the relationship for current in a Series circuit.

• Current is the same at all points in a series circuit.•I1 = I2 = I3

2. What effect does increasing the resistance of a circuit have on the current?

• As resistance increases current decreases.

3. In which position is the voltmeter/ammeter?

A

V

4. Calculate the total resistance.

10Ω

20Ω

5Ω

14410

425.0

1

1

25.02.005.05

1

20

1111

T

T

TTT

R

R

RRR

5. Two identical bulbs are connected in series to a 9V battery.What is the voltage across each bulb?

• 9/2= 4.5V

6. Calculate the power dissipated in a 330Ω resistor when a 5A current flows through it.

• P = I2 R• P = (5)2 x 330• P = 8250W

7. Two identical 10Ω resistors are connected to a 9V supply. What is the current through each resistor?

• R = 10 + 10 = 20Ω• I=V/R=9/20• I = 0.45A

8. State the relationship for voltage in a parallel circuit.

• Voltage in a parallel circuit is equal across each branch.

VT = V1 = V2 = V3

9. What is electrical power?

• The rate at which electrical energy is converted to other forms.

• Energy per second

10. What is the function of a variable resistor?

• To allow you to vary the current in a circuit.

11. Which resistor has a greater potential difference across it?

• The 7Ω resistor.

9V

7Ω 6Ω

12. Calculate the voltage across the resistor.

• Vs = V1 + V2

• 12 = 4 + V2

• V2 = 8V

12V

4V

13. What is current?

•The rate of flow of electric charges around a circuit.• The charge per second that passes a point.

14. What happens to the value of a resistor when the Voltage across it is increased?

• The resistance of a resistor remains constant.

15. Give a practical application of a variable resistor.

• Volume control on radio• Temperature control on cooker• Brightness control on a dimmer switch

16. What is the current through the bulb?

• IT = I1 + I2• 4 = 3 + I2• I2 = 1A

4A

3A

17. What is the total resistance of a 20Ω & 30 Ω resistor in parallel?

12083.0

1

1

083.0033.005.01

30

1

20

11

111

T

T

T

TTT

R

R

R

RRR

18. Calculate the energy used by a 12V kettle in 2minutes if it draws 3A from it’s supply.

• P = IV = 3x12 = 36W

E = Pt E = 36x2x60 E = 4320J

19. What formula relates power, voltage and resistance?

• P = V2/R

20. What is Voltage?

•The energy given to each charge in the circuit.