21. Which of the following is not an expression of power?
A. P = VI
B. P = I2R
C. P = V2/R
D. P = I/R
Answer d
Power is the product of voltage and current. Writing I in terms of V, we get
P = V2/R
writing V in terms of I, we get
P = I2r. [/bg_collapse]
22. Which of the following statements are true?
A. Power is proportional to voltage only
B. Power is proportional to current only
C. Power is neither proportional to voltage nor the current
D. Power is proportional to both the voltage and current
23. A 250V bulb passes a current of 0.3A. Calculate the power in the lamp.
A. 75W
B. 50W
C. 25W
D. 90W
24. Kilowatt-hour (kWh) is a unit of?
A. Current
B. Power
C. Energy
D. Resistance
25. Calculate the power in the 20 − ohm resistance.
A. 2000kW
B. 2kW
C. 200kW
D. 2W
26. A current of 5A flows in a resistor of 2 ohms. Calculate the energy dissipated in 300 seconds in the resistor.
A. 15kJ
B. 15000kJ
C. 1500J
D. 15J
27. Calculate the power across each 20 − ohm resistance.
A. 1000W, 1000W
B. 500W, 500W
C. 1000kW, 1000kW
D. 500kW, 500kW
28. Calculate the power across each 10 − ohm resistance.
A. 1000kW, 1000kW
B. 1kW, 1kW
C. 100W, 100W
D. 100kW, 100kW
29. Calculate the work done in a resistor of 20 ohms carrying 5A of current in 3 hours.
A. 1.5J
B. 15J
C. 1.5kWh
D. 15kWh
30. The SI unit of power is?
A. kW(kilowatt)
B. J/s(joules per seconD.
C. Ws(watt − seconD.
D. J/h(joules per hour