Question

If a lamp has a resistance of 120 omha when it operates at 100 W, what current does it carry?

Answer 1

For this question, we need to know two important formulas.

`I=(V)/(R)`
`P=IV`

With these two formulas, we can solve for current.

In this problem, we are not given voltage, so we will need to solve for voltage in both problems to remove it

V = IR

V = P/I

If we set both equations equal to each other we get

IR = P/I

Since we are solving for current, we need to move I to one side of the equation

I = sqrt(P/R)

Now we can solve with the numbers we have.

I = sqrt(100/120) = .913 amps