Work and Energy Worksheet-3
A. 60 watts B. 3600 watts
C. 600 watts D. 60 kilowatts
A. 3 B. 30 C. 300 D. 3000
A. 9 × 10^{5} joules B. 9 × 10^{6} joules
C. 9 × 10^{8} joules D. 9 × 10^{9} joules
A. increases
B. decreases
C. remains constant
D. first increases and then decreases
A. joule B. newton- metre
C. kilowatt D. kilowatt-hour
A. chemical energy to heat energy
B. kinetic energy to heat energy
C. potential energy to sound energy
D. chemical energy to kinetic energy
A. hydroelectric power stations use water to drive turbines
B. in a power station, turbines drive generators
C. electricity from thermal power stations differs from that produced in hydroelectric power stations
D. in hydroelectric power stations and thermal power stations, alternators produce electricity
A. 0.3 B. 1.2 C. 3.0 D. 6.0
A. only potential energy
B. only kinetic energy
C. half potential and half kinetic energy
D. less potential and more kinetic energy
A. watt B. watt-hour
C. kilowatt-hour D. kilowatt
A. 100 J B. 600 J C. 3600 J D. 6000 J
A. electric motor B. alternator
C. turbine D. electric heater
A. electrical energy into sound energy in ordinary telephone
B. microwave energy into sound energy in a mobile phone
C. sound energy into mechanical energy in a stereo system
D. sound energy into electrical energy in public address system
Answer:
Explanation: Power =
Energy consumed = 7.2 kJ
= 7.2 × 1000 J = 7200 J
Time taken = 2 minutes
= 2 × 60 seconds = 120 s
Power= (7200 J/ 120s)
= 60 J/s
= 60W
Thus, the power of this electric bulb is 60 watts.
Explanation: Power, P = 60 watts
= (60/1000) kilowatts
= 0.06 kW
Time t= 50 h
Now, putting P = 0.06 kW and t = 50 h in the formula :
Power =
0.06 kW =
Energy consumed = 0.06 kW × 50 h = 3kWh
Thus, the electrical energy consumed is 3 kWh or 3 units.
Explanation: 250 units of electrical energy means 250 kWh of electrical energy.
1 kWh of energy = 3.6 × 10^{6} J
250 kWh of energy = 3.6 × 10^{6} × 250 J
= 9 × 10^{8} J
Thus 250 units of electrical energy is equal to 9× 10^{8} joules.
Explanation: Energy can never be created nor destroyed hence the total energy will remain constant.