2.A 5 Ohm resistor is connected to a 9 Volt battery. How many Joules of thermal energy are produced in 7 minutes? 3.The current in a flashlight powered by 4.5 Volts is 0.5 A. What is the power delivered to the flashlight?

4.If the flashlight in the previous problem is left on for 3 minutes, how much electric energy is delivered to the bulb?

7.A 50 Ohm resistance causes a current of 5 milliamps to flow through a circuit connected to a battery. What is the power in the circuit?

8.How many Joules of electric energy are delivered to a 60 Watt lightbulb if the bulb is left on for 2.5 hours?

Explanation:

2 )

power of an electric device = V² / R where V is volts and R is resistance

putting given data

power = 9²/ 5

= 16.2 J/s

energy produced in 7 minutes

= 16.2 x 7 x 60

= 6804J .

3 ) Power of an electrical device

= V² / R

= V X I where I  is current

= 4.5 x .5

= 2.25 W or J/s

4 )

energy used in 3 minutes with power of 2.25 W

= 2.25 x 3 x 60

= 405 J .

7 )

power of a electrical device

= V x I

IR x I  where R is resistance .

= I²R

putting given data

power = .005² x 50

= 1.25 x 10⁻³ W .

8 )

Energy used up by a 60 W bulb in 2.5 hours

= 60 x 2.5 x 60 x 60

= 5.4 x 10⁵ J .

4

explanation:

4

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