Ohm's law word problems

These Ohm's Law word problems will show you how to use the Ohm's Law to solve some basic and simple word problems.

We will use the formula to show how to do the followings:

  • Find the current when the voltage and the resistance are given.
  • Find the voltage when the current and the resistance are given.
  • Find the resistance when the voltage and the current are given.
current =
voltage / resistance

Problem #1:

A frying pan is connected to a 110-volt circuit. If the resistance of the frying pan is 10 ohms, how many amperes does the frying pan draw?

Solution

The voltage and the resistance are given, so we can just use the formula to find the current.

current =
voltage / resistance

current =
110 volts / 10 ohms

Current = 11 amperes.


Problem #2:

When a current of 3 amperes is run through the coiled heating element of a stove, the resistance of the element is 80 ohms. What is the voltage of the stove?

Solution

The current and the resistance are given. We need to use the formula to solve for the voltage or v.


Recall that if 2 =
8 / 4
, then 8 = 4 × 2

Similarly, if current =
voltage / resistance
, then voltage = resistance × current

Voltage = resitance × current = 80 ohms × 3 amperes = 240 volts

Problem #3:

A lightbulb carries 0.5 A when 4 volts is impressed across it. What is the resistance of the filament in the lightbulb?

Solution

The current and the voltage are given. We need to use the formula to solve for the resistance.


Recall that if 2 =
8 / 4

Then, 4 =
8 / 2

Similarly if current =
voltage / resistance


Then resistance =
voltage / current

Resistance =
4 volts / 0.5 A

Resistance = 8 ohms

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