1. The resistance of a flashlight bulb is 240 . What is the current in the bulb

ID: 1453701 • Letter: 1

Question

1. The resistance of a flashlight bulb is 240 . What is the current in the bulb when used with a 6.0 V battery?

2. What is the current in question #1 expressed as mA?

3. What is the power used by the bulb in question #1?

4. What is the maximum voltage that can be applied to a 12.5 k resistor rated at 0.25 W?

5. What is the current in the resistor mentioned in question #4. Express your answer in mA with one decimal place.

6. A light bulb is rated at 60 W when connected to a 120 V source.

a) What current flows through the light bulb in this case?

b) What is the bulb’s resistance?

c) Assuming the resistance stays the same, what would be the current in the current in the bulb if it were connected to a 60 V source?

d) What would be the power used in this case?

1) v = ir

i = 6/240 = 0.025 amp

2) i = 25 mA

3) power = v*i = 6*0.025 = 0.15 watt

4) p = v^2/r

v = sqrt(p*r) = 55.9 volts

5) v = ir

i = v/r = 55.9/12500 = 4.5 mA

6) a) p = v*i

i = p/v = 60/120 = 0.5 amp

b) v = ir

r = v/i = 120/0.5 = 240 ohm

c) 120/0.5 = 60/i

i = 60/240 = 0.25 amp

d) p = v*i = 60*1/4 = 15 watt

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