Regents Physics Parallel Circuits –Ohm’s Law in Parallel Circuits

Parallel Circuits Parallel Circuits Summary 1. The potential drops of each branch equals the potential rise of the source. 2. The total current is equal to the sum of the currents in the branches 3. The inverse of the total resistance of the circuit (also called effective resistance) is equal to the sum of the inverses of the individual resistances.

Parallel Circuit and Ohm’s Law

Voltage in a Parallel Circuit –What is the voltage drop across the resistor and light bulb? –Draw a voltmeter that would measure the potential difference across the resistor only 12 V cell V Answer: 12 VOLTS

Current in a Parallel Circuit Current in divided in the branches Resistance of individual resistors determines how much current will flow through it 12 V cell e-e- e-e- e-e- e-e- e-e- e-e- Question: What has higher resistance the resistor or the light bulb? Draw an ammeter measuring the current through the light bulb the total current in the circuit

Equivalent Resistance A short-cut method to using the equation –Find the average of the resistors –Divide by number of resistors is the same as…

Equivalent Resistance con’t More than 2 resistors is the same as… is approximately… = 24 24/3 = average = 8 8/3 resistors = between 2 - 3

Example of a Parallel Circuit 1) Find current flowing through each resistor 2) Find the total current flowing in the circuit 3) Find the equivalent resistance of the circuit 12V R 1 = 2  R 2 = 3  R 3 = 6 