Electrical Circuits Circuits Components Three main parts of

Electrical Circuits

Circuits Components �Three main parts of a circuit: �Potential �Resistor �Closed Pathway �Potential and pathway are required for there to be a circuit and a resistor is required to make the circuit useful. �There are other “useful” things that can be put in a circuit; we will only talk about resistors.

Potential vs. Current �Potential �The driving force or reason why something wants to move. �Electrical potential is measured in volts (V). �Current �The actual movement of something, as in through a circuit. �Electrical current is measured in amperes (A).

Potential vs. Current �You can have the drive without the movement. �You cannot have the movement without the drive. �You can have potential without current. �You cannot have current without potential!

Two Types of Circuits �Series: �the current must flow through each resistor one after another. Resistors are hooked end to end. �If one resistor goes bad, the circuit is broken and stops working �The current is constant in the circuit.

Two Types of Circuits �Parallel: �the current flows through each resistor simultaneously. Resistors are hooked to each other at BOTH ends. �If one resistor goes bad, that circuit is broken but others keep working �The voltage is constant in the circuit. �Multiple circuits allow for each resistor to be independently attached to the voltage.

Calculations in Circuits �Ohm’s Law �The more voltage you have, the more current you get. � Voltage and current are DIRECLTY related. �The more resistance you have, the less current you get. � Resistance and current are INVERSELY related. �In mathematical form: �V = IR �Voltage = current * resistance

Example of Ohm’s Law �If a light bulb is running at 120 volts and has a current of 0. 5 amps, what is the resistance in the bulb? �Voltage (V) = 120 volts �Current (I) = 0. 5 amps �Resistance (R) = ? ? �Substitute in what you know: �V = IR � 120 = 0. 5(R) �R = 240 Ω (ohms) �The unit of resistance is Ohms (Ω)

Power and Energy �In a circuit, you can also calculate the power and energy. �Power = Voltage * Current �P = IV �Power = Energy / time �P = E/t �The units of Power are Watts (W) �The units of Energy are Joules (J) or kilowatt hours (k. Wh) �Power is how fast energy is transferred.

Power Calculation �Our same light bulb from before (@ 120 V and 0. 5 amps) has been on for three days. What is its power rating and how much energy did it use? �Power = Voltage * Current (P = IV) �P = (120)(0. 5) = 60 Watts (W) �Power = Energy / time (P = E/t) � 60 = E/3 E = 180 W-days � 180 W-days * 24 hrs / 1000 k. W = 4. 32 k. W-hrs