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## Homework Statement

This is a 3-part problem of which I have solved 1 and 2. I've included here just so you can follow the problem. A 50-watt lamp, a 20-watt, a 75 watt lamp, and a 100-watt lamp are connected in parallel to a 110-volt circuit. Calculate a) the current through each lamp; b) the resistance of each lamp; c) the total resistance of the circuit.

## Homework Equations

## The Attempt at a Solution

a.) Current is calculate by I=P/V where P is in Watts so

I=50/110 = .45 A

I=20/110 = .18 A

I=75/110 = .682 A

I=100/110=.91 A

b.) Here we use Ohm’s Law again: R = V / I

For 50 Watt lamp R=110/.45 = 244.4 Ω

For 20 Watt lamp R=110/.18 = 611 Ω

For 75 Watt lamp R=110/.682 = 161.29 Ω

For 100 Watt lamp 110/.91 = 120.88 Ω

**c.)To find total resistance of the circuit in parallel, use**

**R=1/(1/244.4) + (1/611) + (1/161.29) + (1/120.88) = 49.5 Ohms**

**I've seen many ways to calculate resistance - but is it accurate to do it this way for a parallel circuit?**