ELECTRICAL CIRCUITS Batteries are composed of terminals cells

ELECTRICAL CIRCUITS

• Batteries are composed of terminals, cells and electrodes.

Batteries • Every battery has two terminals. One terminal is (+), positive, the other is (-), negative. • In an AA, C or D cell (for flashlights), the ends of the battery are the terminals. • In a large car battery, two heavy lead posts are the terminals.

• The “cells” are filled with chemicals. In a D cell battery, the chemical is a paste. Ina car battery, the cells are filled with a liquid chemical.

Battery Cutaway

Operation • Electrons from the chemicals collect on the negative terminal of the battery. • Forming a connection with a wire, between negative and positive terminals, causes electrons to flow from the negative to the positive terminal, rapidly. Remember, Opposites attract!

• Some type of load is connected to the wires, such as a light bulb, a motor or an ipod.

Volta • In a battery, a chemical reaction produces electrons. The speed of electron production by this chemical reaction controls how many electrons can flow between the terminals. • The first battery was created by Alessandro Volta in 1800.

He stacked alternating layers of zinc, blotting paper soaked in salt water, and silver.

Typical battery application & Connection

The CELL The cell stores chemical energy and transfers it to electrical energy when a circuit is connected. A battery is also known as a cell. The cells chemical energy is used up pushing a current round a circuit.

Electric Currents An electric current is a flow of electric charges.

What is an electric current? An electric current is a flow of microscopic particles called electrons flowing through wires and components. + - The current flows from the Negative terminal to the Positive terminal of a cell.

A circuit is the path that is made for an electric current.

simple circuits A circuit MUST HAVE a load, cell, and wires. A switch can be included but is optional in an electric circuit. cell switch wires load

simple circuits When the switch is closed, the lamp lights up. This is because there is a continuous path of metal for the electric current to flow around. If there were any breaks in the circuit, the current could not flow.

circuit diagram Scientists usually draw electric circuits using symbols; cell Lamp/load switch wires

types of circuit There are two types of electrical circuits; SERIES CIRCUITS PARALLEL CIRCUITS

SERIES CIRCUITS The components are connected end-to-end, one after the other. They make a simple loop for the current to flow round. If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.

Series Circuit • A circuit that only has one path for current to flow through is called a series circuit.

If the path is broken, no current flows through the circuit.

In a series circuit, the same current passes through each element. Disconnect one of the bulbs and the circuit is broken (other bulbs go out). 03 -Oct-20

PARALLEL CIRCUITS The components are connected side by side. The current has a choice of routes. If one bulb ‘blows’ there will still be a complete circuit to the other bulb so it stays alight.

Parallel Circuits • A type of circuit that has more than one path for current is called a parallel circuit.

If one part of the path is removed, the current continues to flow through the other paths of the circuit.

measuring current Electric current is measured in amps (A) using an ammeter connected in series in the circuit. A

measuring current SERIES CIRCUIT • current is the same at all points in the circuit. 2 A 2 A 2 A PARALLEL CIRCUIT • current is shared between the components 2 A 2 A 1 A 1 A

measuring voltage The ‘electrical push’ which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeter V

series circuit • voltage is shared between the components 3 V 1. 5 V

parallel circuit • voltage is the same in all parts of the circuit. 3 V 3 V 3 V

Parallel Circuit Same voltage on each bulb; current splits through each branch. Disconnect one of the bulbs and the other bulbs stay light with same brightness. 03 -Oct-20

Electrical Resistance Current depends not only on the voltage but also on the electrical resistance of the conductor. The wider the wire is, the less the resistance. A short wire offers less resistance than a long wire. Jumper cables use thick wires so as to minimize the electrical resistance. More water flows through a thick hose than through a thin one connected to a city's water system (same water pressure).

Electric Shock The damaging effects of shock are the result of current passing through the body. Effects of Electric Shock on Human Body 03 -Oct-20 Current (A) Effect 0. 001 Can be felt 0. 005 Is painful 0. 010 Causes involuntary muscle contractions (spasms) 0. 015 Causes loss of muscle control 0. 070 If through the heart, serious disruption; probably fatal if current lasts for more than 1 s

Fuses & Circuit Breakers Fuse is designed to melt (due to ohmic heating) when current is too large. Circuit breaker does same job without needing replacement; flip the switch to reconnect. Fuse Circuit Breaker 03 -Oct-20

Would This Work?

Would This Work?

Would This Work?

One More FINAL Thing: • DC—Direct Current-Current only flows in one direction. • AC—Alternating Current flows back and forth (alternates).