# electrical problem

• May 2nd 2007, 04:34 PM
rcmango
electrical problem
Four 18 W lamps are connected in parallel across 6V. Draw the circuit.

What is the current through each lamp? What is the resistance of each?

What is effective resistance of the combined four lamps?

• May 3rd 2007, 11:08 AM
CaptainBlack
Quote:

Originally Posted by rcmango
Four 18 W lamps are connected in parallel across 6V. Draw the circuit.

What is the current through each lamp? What is the resistance of each?

What is effective resistance of the combined four lamps?

See attachment.

The voltage accross each lamp is the same and 6V. So the current through
eash lamp is given by P = IV, here 18 = I.6, so I = 3 Amps.

Ohms law for a single lamp tells us that V=IR, so R=18/3 = 6 Ohms.

The total current supplied by the battery is 4 times the current through the
individual bulbs, so is 12 Amps. Now apply Ohm's law to the entire circuit to
get: 18 = 12.R, so R=1.5 Ohms is the resistence of the combined four lamps.

RonL
• May 3rd 2007, 06:03 PM
rcmango
excellent diagram, thats how i was seein it. THankyou.