2.5 Electrical energy and Power

A lamp changes __________ energy into light energy.

• Kinetic
• Electrical
• Sound
• Chemical

Tags

NGSS.HS-PS3-3

What is the unit of electrical power?

• watt, W

• volt, V

• ampere, A

• ohm, Ω

Tags

NGSS.HS-PS3-2

A bulb of 100 W means that it will consume electrical energy at the rate of:

• 100 kJ per second.
• 100 kJ per hour.
• 100 joules per second.
• 100 joules per hour.

What will be the current drawn by an electric bulb of 1000 W when it is connected to a source of 220 V?
Remember: I = P/V

• 4.55 A
• 28800 J or 28.8 KJ
• 80 W
• 200 W

A current of 4 A flows through a 20 V car headlight bulb. Calculate the electric power.
 
Remember: I=P/V

• 80 W
• 200 W
• 2.5 A
• 4.55 A

Calculate the electric power of an electrical appliance of 20 V having a resistance of 10 ohms.
 
Remember: I=V/R and P=VI

• 200 W
• 40 W
• 2.5 A
• 79.20 KJ

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

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 unit of energy costs $1.20.

• 66 kWh = 66 units; $79.20
• 45 kWh = 44 units; $52.80
• 22.5 kWh = 22.5 units; $27.00
• 80 kWh = 80 units; $96.00

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