Ohm’s Law This formula shows the relationship between current, voltage and resistance. Voltage (Volts) Current (Amps) Resistance (Ohms, )

Ohm’s Law One volt causes a current of 1 amp to flow through a resistance of 1 ohm

Joules per second is watts. Work, Energy, and Power Electrical Power – The rate at which energy is flowing Voltage (Volts) Current (Amps) Power (Watts) Remember Power is the rate of work over time. Joules per second is watts. Voltage (Volts) X Current (Amps) = Power (Watts)

Parts of a Circuit Diagram

More Electric Circuits There are two basic types of circuits: Series Circuits and Parallel Circuits Two bulbs in a parallel circuit. Two bulbs in a series circuit.

Open Circuit When a circuit is broken and electricity no longer flows.

Short Circuit A circuit path with little or no resistance. This releases the complete amperage of the battery all at once. Short Circuit

Series Circuits Series – A circuit in which the current can take only one path. If one component fails in the circuit, the circuit is dead. The current is the same throughout a series circuit.

Series Circuits Resistance is additive in a series. Equivalent (total) resistance is the sum of the resistors in the circuit. Req= R1 + R2 + R3 … Adding resistance in a series. Total resistance = 1 + 1 + 1 = 3 

Kirchhoff’s Voltage Law Around any closed circuit, all of the voltage changes must add up to zero. If the resistors are the same then you can find the voltage drop by dividing the total voltage by the number of resistors. Otherwise you will need to measure the drop with a voltmeter (like the lab) Each resistance drops the voltage. -0.5 V 1.5 V 0.5 V 1.0 V 0 V

Voltage Drops in a Circuit 3 Volts 3 Volts 2 Volts 1 Volts 0 Volts

Parallel Circuits Parallel – A circuit in which the current can take more than one path. There is at least one branch where the current can split up. So, if one component fails, the other components will keep on working The voltage is the same across each device.

Kirchhoff’s Current Law If current flows into a branching point in a circuit, the same total current must flow out again. Voltage remains constant on all branches. If the resistors are the same then you can find the current in each branch by dividing the total current by the number of resistors. Otherwise you will need to measure the drop with an ammeter (like the lab)

Resistance in a parallel circuit Equivalent resistance for a parallel circuit is less than the resistance of each component. (inversely proportional to current) Since there are more pathways to alleviate the resistant pressure of the current, the combined resistance is less. Req= R1 R2 or 1 = 1 + 1 + 1 … R1 + R2 Req R1 R2 R3

Are Holiday Lights Series or Parallel? Series Circuit One Path Parallel Circuit More than one Path

How you prefer your house be wired; Series or Parallel?