Watt’s Law Practice
Problem #1
A typical lightbulb uses 0.83A of
current.
If it is connected to a 120V outlet,
how much power does it use?
Problem #1 Answer
P = 100 Watts
Problem #2
A 110V power supply is hooked up
to a speaker that uses 200W.
How much current does it use?
Problem #2 Answer
I = 1.8 Amps
Problem #3

A 1000 resistor connected to a
6V power source will
produce__________ A of
current and use ___________
Watts of power.

Hint: Use Ohm’s law for the 1st
answer!!
Problem #3 Answer
I = 0.006A or 6mA
P = 0.036 Watts
Problem #4

A 300, 0.25 Watt resistor can
be connected to a voltage
source as high as ___________
without exceeding its wattage
rating.
Problem #4 Answer
V= 8.66V
Problem #5

A 200 resistor conducting
0.05A will use up _________
Watts of power
Problem #5 Answer
P = 0.5 W
Problem #6

The maximum voltage that can
be applied to a 0.5W, 1200
resistor without exceeding its
wattage would be
________volts.
Problem #6 Answer
V=24.5V
Problem #7

The maximum voltage that can
be applied to a 1200, 1/4W
resistor without exceeding its
wattage rating would be
_________volts.
Problem #7 Answer
V= 17.3V
Problem #8

A 9000 resistor conducting
1.2A will use up _________
Watts of power.
Problem #8 Answer
P = 12,960 Watts
Problem #9
A car battery causes a current of
2A through a light and produces
12V across the light.
What is the power used by the
light?
Problem #9 Answer
P = 24 Watts
Problem #10
A flashlight bulb is rated for 0.9
Watts.
If the voltage on the bulb is 3V,
how much current goes through
it?
Problem #10 Answer
I = 0.3A
Homework Problem #1

A 60W light bulb in a lamp is
connected to a 120V outlet.

How much current does it use?
Homework Problem #2

A typical 1200W microwave
uses 11A of current.

How much voltage must it be
using?
Homework Problem #3

An 1800 Ohm resistor can take
up to 4.5W of power.

How much voltage does it use?
How much current does it use?
