Electrical Power and Energy

What is the unit of electrical power?

• watt
• volt
• ampere
• ohm

One megawatt is equivalent to:

• 10² W
• 10⁶ W
• 10²⁴ W
• 10⁸ W

Calculate the electrical energy consumed when a potential difference of 5 V is applied across a resistor of 2 ohms for 30 minutes.
 
Remember: V=IR and I=V/R

• 80 W
• 200 W
• 22500 J or 22.5 KJ
• 4500 J or 4.5 KJ

A current of 0.5 A flows through a resistance of 10 ohms for half an hour. Find the amount of electrical energy consumed by the resistance.
 
Remember:
V = IR
P = VI
E = Pt

• 22500 J or 22.5 KJ
• 4500 J or 4.5 KJ
• 79.2 W
• 2.5 A

Tags

NGSS.HS-PS3-1

An electric meter reads 3462 kWh at the end of the month while a month ago it read 3396 kWh. How many units of electrical energy have been comsumed during the month? Find the cost of electrical energy consumed if 1 kWh of energy costs $0.12

• 66 kWh = 66 units; $7.92
• 45 kWh = 44 units; $5.280
• 22.5 kWh = 22.5 units; $2.700
• 80 kWh = 80 units; $9.600

Tags

NGSS.HS-PS3-1

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 flashlight bulb with a potential difference of 4.5 V across its filament has a power output of 8.0 W. How much current is in the bulb filament? 

• 3.7 A
• 0.23 A
• 1.8 A
• 0.56 A

What is the potential difference across a resistor that dissipates 5.00 W of power and has a current of 5.0 A?  

• 1.0 V
• 4.00 V
• 0.20 V
• 125 V

An electric appliance labelled 80 W.
What does the label means?

• The rate of change of power is 80 W
• The rate of change of energy is 80 J/s
• The rate of change of current is 80 A
• The rate of change of voltage is 80 V

An electric appliance is labelled 2 V, 4 W.
How much electrical charges flow through the electric appliance in 9 minutes?

• 2 C
• 8 C
• 540 C
• 1 080 C