Electromagnetism Concepts: The Motor Effect Induction

The Motor Effect 04/04/2019 Aim: To use Flemming’s Left Hand Rule To explain how a motor works To construct a motor

Fields Bar Magnets handout

Opposite Poles

Same Poles

Fields due to Current

Single Coil of Wire Solenoid

Magnetic Field Lines Movie There are magnetic field lines around every Electrical wire (with current flowing through it) Anything magnetic in the field will experience a force Movie

Wire in a magnetic field Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This virtual experiment can be used as an introduction to the motor effect or as a revision exercise.

The Catapult (Motor) Effect

Motor Effect If a conductor carrying an electric current moves through magnetic field lines at right angles it will experience a force. A charged particle will experience the same effect

Fleming's left hand rule

Demo with Motor Effect Apparatus Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes Students should be made aware that the direction of a magnetic field is usually taken as being N-S rather than S-N, and the direction of current is the direction of conventional current, i.e. positive to negative.

Increasing the Size of the Force Boardworks GCSE Additional Science: Physics Motors and Generators

The motor effect: true or false? Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This true-or-false activity could be used as a plenary or revision exercise on the motor effect, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

Exam Question

Exam Question

Coil in a Magnetic Field Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This activity extends the idea of a current-carrying wire in a magnetic field from slide 4, and introduces the concept of current-carrying coil experiencing rotational force. Students could be asked to interpret the movement of the coil using Fleming’s left-hand rule, and begin to think about how an electric motor works.

How does an electric motor work? Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This activity extends the idea of a simple current-carrying coil rotating in magnetic field from slide 8, and explains how a split-ring commutator enables a coil to continue rotating. Students could again be asked to interpret the movement of the coil using Fleming’s left-hand rule.

Boardworks GCSE Additional Science: Physics Motors and Generators Demo Motor Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes Students should be made aware that the direction of a magnetic field is usually taken as being N-S rather than S-N, and the direction of current is the direction of conventional current, i.e. positive to negative.

DC electric motor simulation Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This simulation takes the concepts from the previous slide to create an animated motor simulation. The current, forces and magnetic field can be toggled on and off, to aid visualization and understanding, and the speed and direction of rotation can be altered.

How do we increase motor strength? Boardworks GCSE Additional Science: Physics Motors and Generators How do we increase motor strength? Would the same strength motor be used in both of these? How can the strength of an electric motor be increased? Photo credits: © 2007 Jupiterimages Corporation increase the current flowing through the coil increase the strength of the magnet increase the number of turns on the coil Worksheet

The Motor Effect recap Aim: To use Flemming’s Left Hand Rule To explain how a motor works To construct a motor

Induction 04/04/2019 Aim: To observe and define induction To explain how electricity is generated

Exam Question

Exam Question

Inducing current in a wire Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This virtual experiment can be used as an introduction to electromagnetic induction or as a revision exercise.

What is electromagnetic induction? Boardworks GCSE Additional Science: Physics Motors and Generators Current Carrying Wire + Magnetic field = Motion Motion + Magnetic field = Current in Wire Changing Magnetic field = Current in wire If they are at right angles to each other

Inducing current in a coil Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This virtual experiment can be used as an alternative introduction to electromagnetic induction or as a revision exercise.

Boardworks GCSE Science: Physics Electricity to the Home Induction Boardworks GCSE Science: Physics Electricity to the Home If a magnet is moved near a coil of wire a current is induced in the wire Faster motion, bigger current Stronger magnet, bigger current More turns, bigger current Change direction of motion, change direction of current

Factors affecting induced current Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes Appropriately coloured voting cards could be used with this classification activity to increase class participation.

How can motion produce a current? Boardworks GCSE Science: Physics Electricity to the Home Teacher notes This true-or-false activity could be used as a plenary or revision exercise on electromagnetic induction, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

Boardworks GCSE Additional Science: Physics Motors and Generators What are Generators? Boardworks GCSE Additional Science: Physics Motors and Generators A generator is a device that converts mechanical energy into electrical energy. It is the opposite of an electric motor. Power stations use generators to produce electricity on a large scale. Mechanical energy is provided by rotating turbines that can be powered by: high-pressure steam – in coal, oil, gas and nuclear power stations wind – in wind turbines falling water – in hydroelectric power stations Photo credit: Clipper Windpower / National Renewable Energy Laboratory

How do AC generators work? Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This activity extends the idea of simple electromagnetic induction from slides 16 and 19, and explains how slip rings enable a generator to produce alternating current.

AC generator simulation Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This simulation takes the concepts from the previous slide to create an animated generator simulation. The current, forces and magnetic field can be toggled on and off to aid visualization and understanding.

Induction: true or false? Boardworks GCSE Additional Science: Physics Motors and Generators Teacher notes This true-or-false activity could be used as a plenary or revision exercise on electromagnetic induction, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Coloured traffic light cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

What is a transformer? iron core secondary coil primary coil The voltage of an alternating current can be changed using a device called a transformer. A transformer contains two coils that are wound around a soft iron core. iron core The alternating current in the primary (input) coil produces an alternating magnetic field. This alternating magnetic field induces an alternating current in the secondary (output) coil. secondary coil primary coil

How does a transformer change voltage? The voltage induced in the secondary (output) coil depends on the number of turns on the primary and secondary coils. A step-up transformer has more turns on the secondary coil and so increases voltage. A step-down transformer has fewer turns on the secondary coil and so decreases voltage.

How are transformers used to supply electricity?

Transformers Worksheet Transformers are used to change the voltage from the Primary (input) to the Secondary (output) They only work with a.c. (alternating current) Input (Primary) Voltage = Number of Primary Turns Output (secondary) Voltage Number of Secondary Turns Example Question: Input voltage = 230 V Primary turns = 10000 Secondary turns = 500 What is the secondary voltage? Worksheet