- Slides: 28
Electric Field, Electric Current and Electrical Circuit
Electric Field • is a region in which an electric charge experiences a force. • it is represented by lines that indicate the direction of force. + Away from the positive charge Towards the negative charge -
Two similar charges repel each other
Closer field lines indicate a stronger electric field. Two opposite charges attract each other. Field lines that are further apart indicate a weaker electric field.
Effect of an Electric Field + + + + + - - - ++ + + - + - - The flame is spread out more to the negative plate as the positive charges are heavier than the negative charges.
Heat energy from flame + - Ionisation Negative Plate + Positive Charge - Negative Charge Air Molecule Positive Charge
Electric Current Definition: An electric current is the rate of flow of electric charges in a circuit. electric cell connecting wire filament flow of electrons Charge Conductor Cross-sectional area
How does electricity flow? • The battery in a circuit gives energy to the electrons and pushes them around a circuit, from the negative terminal of the cell, round the circuit and back to the positive terminal of the cell.
How to Measure Current? • The SI unit for electric current is ampere (A). • Smaller currents are measured in milliamperes (m. A). 1 A = 1, 000 m. A 1 m. A = 0. 001 A • Different electrical components and appliances require different sizes of current to turn them on.
Instrument to Measure Current • An ammeter is an instrument used for measuring electric current.
Ammeter • It must be connected in series in the circuit. • Positive side of ammeter must be connected nearest to the positive terminal of the battery (electric cell), and vice versa.
Electric Circuits • Electric circuits are made up of electrical components • These components must be joined together without any gap in between to form a closed circuit. connecting wires electric cell light bulb Note: circuit board Components refer to the light bulb, wires, battery
Electric Circuits • Incomplete circuits are called open circuits. connecting wire is missing no source of electrical energy Both the circuits in the diagram are incomplete, hence they are known as “open circuits”.
A n electric c u r r e n t f l o w s o n l y w h e n t h e r e is: • a source of electrical energy and • a closed circuit connecting wires electric cell light bulb circuit board
How to draw Circuit Diagrams Component Symbol Component + An electric cell Symbol + Battery Switch (open) Light bulb (lamp) Connecting wires (not joined) Switch (closed) Connecting wires (joined) Symbols are used to represent the various electrical components in circuits.
Can you predict how this circuit would looked like in its schematic format?
Switches A switch is used to open or close a circuit. Main switch used i n buildings Switches used on circuit boards
Series a n d P a r a l l e l There are 2 ways inwhichanelectriccircuitcan be arranged: 1. Series 2. Parallel
Series C i r c u i t • A series circuit connects the components one after the other • A single loop is formed • A break in any part of a series circuit stops the flow of current in the whole circuit.
Parallel Circuit • A parallel circuit divides into two or more branches. • The current divides and flows through each parallel branch. • If a component breaks or is removed, the other components remain on.
W h i c h of t h e f o l l o w i n g i s a series c i r c u i t ? W h i c h is a parallel circuit? Series Circuit Parallel Circuit
Draw the circuit diagram for the f o l l o w i n g set up a n d s t a t e w h e t h e r i t i s a series o r p a r a l l e l c i r c u i t.
Draw the circuit diagram for the following set up and state whether it is a series or parallel circuit.
W h i c h i s brighter?
W h i c h of t h e f o l l o w i n g i s a series circuit? W h i c h is a parallel circuit? Series Circuit Parallel Circuit