1. A battery and a light bulb are connected in series so a current flows through

Question

1. A battery and a light bulb are connected in series so a current flows through the light bulb. The battery provides a constant voltage of 12 Volts. The light bulb has a Power output of 30 Watts once the filament has reached its final temperature.

a) What is the current drawn from the battery by the light bulb?

i = 2.5A

b) What is the resistance of the filament of the light bulb?

R = 4.8 Ohms

c) If the battery has a capacity of 1250 milliamp-hours, i.e. it can deliver 1 mA for 1250 hours or equivalently 1250 mA for 1 hour before it is out of charge, how long in would the battery last assuming a constant rate of energy delivered to the bulb?

t = 1/2hr

Explanation / Answer

p = VI

30 = 12 x I

I= 30/12 = 2.5A

b) R= V/I

=12/2.5

=4.8 ohms

c) t=1.250x60/2.5

= 30 min

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