Starter - A.C and D.C electricity 1.Draw diagrams to help you explain the difference between A.C and D.C electricity. 2.A.C or D.C. providers? Battery generator Solar cell 1.Draw diagrams to help you explain the difference between A.C and D.C electricity. 2.A.C or D.C. providers? Battery generator Solar cell

P6 – Electricity for Gadgets Lesson 11 – The Dynamo effect Learning aim: Demonstrate an understanding of how a current and voltage can be induced in a wire

Learning Objectives Success Criteria Understand how a dynamo generates electricity. Understand how a voltage is induced. Understand how changes in magnetic field affect induced voltage. Describe and recognise the dynamo effect and how electricity can be generated.(Grade E-D) Label a diagram of an a.c. generator showing the coil, magnets, slip rings and brushes. (Grade E-D) Understand the interaction between a wire carrying current and magnetic field.(Grade C) Explain what affects the size of the induced voltage (Grade C-A)

AC/DC What is AC? AC is alternating current, a current which is constantly changing in direction. What is DC? DC is direct current, current that is always flowing in one direction. Source of AC? Mains electricity (50Hz) Sources of DC? Cells or batteries

Electromagnetic Induction N The direction of the induced current is reversed if… 1)The wire is moved in the opposite direction 2)The field is reversed The size of the induced current can be increased by: 1)Increasing the speed of movement 2)Increasing the magnet strength

Flemings Right Hand Rule

What effects the size of the induced voltage? Name the three things that effect the size of the induced voltage : 1) The strength of the magnetic field 2) The speed the wire cuts magnetic field lines 3) The length of the wire (in the field) HT

Electromagnetic induction

The direction of the induced current is reversed if… 1)The magnet is moved in the opposite direction 2)The other pole is inserted first The size of the induced current can be increased by: 1)Increasing the speed of movement 2)Increasing the magnet strength 3)Increasing the number of turns on the coil

AC Generator (P6f01 Q1) Look at the diagram of a generator. Add the labels and describe the purpose of each of the key parts (use p252 to help) Magnetic poles Coil Brushes Slip ring commutator

WS answers Q1a magnet and wire with relative movement Q1b – see diagram on page 252 of the Student Book for labels Q1c N on left, S on right Q1d generator produces a.c. an electric cell d.c.

Flemings Right Hand Rule What do these represent? What is electromagnetic induction used for in the real world?

Moving Coil Microphone How does the microphone work? plenary

Learning Objectives Success Criteria Understand how a dynamo generates electricity. Understand how a voltage is induced. Understand how changes in magnetic field affect induced voltage. Describe and recognise the dynamo effect and how electricity can be generated.(Grade E-D) Label a diagram of an a.c. generator showing the coil, magnets, slip rings and brushes. (Grade E-D) Understand the interaction between a wire carrying current and magnetic field.(Grade C) Explain what affects the size of the induced voltage (Grade C-A)

Electromagnetic induction What will happen if you move a magnet into a coil of wire? A current is induced in the coil. Only when the magnet is moving.

Stationery magnet What happens when the magnet is in the coil? Nothing!! A current is only induced when the magnet is moving.

Electromagnetic induction What will happen if you move the magnet out of the coil of wire? A current is induced in the coil. This time in the opposite direction. If you reverse the direction of the movement, then you reverse the direction of the current.

AC or DC? What will happen if you move a magnet in and out of the coil repeatedly? A current will be induced in the coil, the current will flow in one direction and then reverse and flow in the opposite direction. What type of current is this? Alternating current Plenary

Answer these questions? in your book What happens when the wire is moved through the magnetic field What does the ammeter show you The current is called an ……………………… Current Who discovered how to make electricity using magnetism Which direction is the current flowing?

Lenz's law : The direction of the induced current is such that it opposes the change producing it