Electrical Systems

VOCABULARY OBJECTIVES Series circuit Voltage drop Kirchoff’s Voltage

Law

• Describe a series circuit.

• Calculate the resistance and current in a series circuit.

• Explain how the voltage changes across each resistor in a series circuit.

• A series circuit has one path A series circuit contains only one path for

electric current to flow. The current is the same at all points in the

circuit.

• Stopping the current If there is a break at any point in the circuit,

the current will stop. Ex. Holiday Lights

• Using series circuits Devices are connected in series for specific

purposes. Ex. switches

Use Ohm’s Law You can use Ohm’s law to calculate the

current in a circuit if you know the voltage and resistance.

Adding Resistances Rtotal = R1 + R2 + R3 + …

Ignoring resistances Everything has some resistance, even

wires. However, sometimes the resistance of

an object is so small that we can ignore it when compared to other objects.

Energy changes forms Energy cannot be created nor destroyed Devices in a circuit convert electrical

energy Voltage decreases after each device that

uses power, known as voltage drop. Voltage drop is the difference in voltage

across an electrical device. Charges lose their energy

The current in a series circuit is the same everywhere.

As power gets used, the voltage gets lower.

Voltage If three bulbs are identical each gives off

the same amount of light and heat. Each uses the same amount of power.

• Voltage drops– Each separate bulb or resistor creates a

voltage drop.– Voltage drop across a bulb is measured

by an electric meter.– The greater the voltage drop, the

greater the amount of power being used per amp of current flowing through the bulb.

• Ohm’s Law– Voltage drop across a distance is

measure by Ohm’s Law.

Energy conservation The Law of Conservation of Energy also

applies to a circuit. Over an entire circuit, the power used by

all the bulbs must equal the power supplied by the battery.

The total of all the voltage drops must add up to the battery’s voltage, known as Kirchoff’s voltage law.