3.4 Electrical Energy and Power

A current of 5A flows in a heating elements for 10 minutes. If the potential difference across the elements is 240 V, calculate the electrical energy is used by the elements

• 12kJ

• 7.2 kJ
  

• 720 kJ
  

• 2.4kJ

The power of an appliance is...

• the amount of voltage going through it 
• the amount of energy transferred per second
• the amount of charge that passes through per second

Watts is the same as...

• Joules per second
• Voltage per second
• Current per second

a pair of 15-watt computer speakers are connected to a 12-volt power supply. what is the electric current running through the speakers? 

• 1.25 A
• 0.8 A
• 12.5 A
• 180 A

A bulb is labelled 6 V, 0.6 A. What is the power of the bulb?

• 0.6 W

• 5W

• 3.6W

• 6W

A filament bulb is labelled 240 V, 60 W. What is the current flows through the filament and the resistance of the filament?

• 0.25A, 60Ohm

• 0.25A, 960 Ohm

• 4.00 A, 60Ohm

• 4.00A , 240 Ohm

The kilowatt - hour is a unit of

• Energy

• power

• Charge

• Voltage

A television is labelled 250 W , 240 V is used 5 hours per day in one month. If the cost of electricity is 24 sen per unit , what is the cost of operating the appliance in the month of June?

• RM 5.00

• RM 6.00

• RM 8.00

• RM 9.00

The table above shows the electricity tariffs for domestic use. The reading of an electricity meter reading in a house in the month of August is 6020 and in the month of September is 7450. What is the cost of electricity is used in the house ?

• RM 420

• RM228

• RM168

• RM374

A fluorescent lamp with a power rating of 40 W produce

36 W of light energy. What is the efficiency of the lamp?

• 90%

• 10%

• 36%

• 40%