1) An electric circuit is a complete path that allows electric current to flow. A battery acts as a pump to push current through the circuit. 2) There are two basic types of circuits: series circuits where current flows through components one after another, and parallel circuits where current divides among branches. 3) Circuit diagrams use symbols to represent components and show connections using straight lines meeting at right angles. Voltmeters measure voltage in parallel, ammeters measure current in series. Fuses and circuit breakers prevent overloading.

1. Electric Circuits

2. 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

3. 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?

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

5. Circuit Diagramming
 Shorthand method of drawing circuits
• Must use symbols.
• Wires are drawn in straight lines.
• Wires meet at 90° angles.

6. Measuring Voltage and Current
When measuring voltage, the volt meter
needs to be hooked in parallel to the
circuit.
R2 R3
R4
R1

7. Measuring Voltage and Current
When measuring amperage, the
am meter needs to be hooked in series
to the circuit.
R1 R2 R3

8. Overloading  too much current is drawn out
causing the wires to heat up
Only happens in parallel circuits
Use Fuses or Circuit Breakers
Electromagnets that
open a switch
interrupting the flow of
Piece of metal that current
melts at a certain
current opening
the circuit

9. • 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)

10. • 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