Electric Circuits

Circuit

Circuit

complete (closed) path along which a charge may flow similar to a closed set of pipes with H2O Battery acts as a pump

2 Basic Types of Circuits

1.Series Circuits Everything is lined up in a row current goes through a single path current is resisted by each individual

device

What happens if one device fails?

2. Parallel Circuits Everything is lined up separately Voltage is the same across each device Current divides among the branches

Circuit Diagramming Shorthand method of drawing circuits

• Must use symbols.

• Wires are drawn in straight lines.

• Wires meet at 90 angles.

Measuring Voltage and Current

When measuring voltage, the volt meter needs to be hooked in parallel to the circuit.

R1

R2 R3

R4

Measuring Voltage and Current

When measuring amperage, the am meter needs to be hooked in series to the circuit.

R1 R2 R3

Overloading too much current is drawn out causing the wires to heat up

Only happens in parallel circuits

Use Fuses or Circuit Breakers

Piece of metal that melts at a certain current opening the circuit

Electromagnets that open a switch interrupting the flow of current

• To find resistance of a circuit with resistors in series just add all the resistors. R1 + R2 + Rx …. = Requivalent

• Example: three resistors of values 30 ohm, 40 ohm, and 50 ohm are connected in series to a 12 V battery. What is the equivalent resistance? Circuit Current?

• 30 + 40 + 50 = 120 Ohm

• Use the Requivalent , the given voltage, and Ohm’s Law to find the current through the whole circuit.

• V = IR 12 = I x 120 12/120 = .1 Amps• Use V = IR to find the voltage through each resistor.

• V1 = .1(30) V2 = .1(40) V3 = .1(50)

• Add all the voltages 3 + 4 + 5 = 12 V (original)

• To find equivalent resistance of resistors in parallel add the inverses of each resistor and take the inverse of the answer.

• 1/R1 + 1/R2 + 1/Rx… = 1/Requivalent

• Example: Three resistors are connected in parallel to a 12 Volt battery as follows, 30 Ohm, 40 Ohm, and 50 Ohm. Find the equivalent resistance and the current through the circuit.

• Use x-1 on your calculator.• 1/30 + 1/40 + 1/50 = 1/R 1/R = 12.76 Ohms • V = IR to find current through circuit• 12 = I(12.76) 12/12.76 = .94 Amps

• Use V = IR to find current through each resistor • 12 = I(30) 12 = I(40) 12 = I(50)

• .4 + .3 + .24 = .94 Amps