ELECTRIC MOTOR

GENERATOR EFFECT

• When the magnet is moved inside and outside of the wire it produces a current in the wire due to electromagnetic induction.
• If the magnet is moved in the opposite direction the deflection is in the opposite direction
• Moving the wire or moving the coil has the same effect as both cuts the magnetic field lines.
• When the wire is connected to a built it will light up = GENERATOR EFFECT

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ALTERNATING CURRENT GENERATOR

• A coil is rotated in a magnetic field.
• Rotating coil cuts the magnetic field of lines and produces an electric current through electromagnetic induction.

DYANAMO

• Motor has slip ring commutator instead of slip rings
• So due to this commutator the current is not reversed so it gives only DC current.

•                      Split ring commutator

                                        Coil of wire connected to alternating current

Current is switched on it generated a magnet field which interact with the permanent magnetic field and produces force. When the current reverses the direction of force reverses generating sound waves. Banner 8

TRANSFORMERS

It is the device which is used to increase (step up) or decrease the voltage (step down) or the potential difference.

• Primary coil and the secondary coil is wound around the soft iron core.
• Primary coil is connected to an AC supply.

Input Voltage

• Changing Electric current in the primary coil creates a magnetic field.
• The changing magnetic field cuts along the secondary coil and produces a voltage.

Output Voltage

TRANSFORMER CALCULATIONS

 =  VP/VS=NP/NS Vp = Voltage across primary coil Vs = Voltage across secondary coil Np = Number of turns in primary Ns = Number of turns in secondary If the number of turn in primary is 20 and input voltage is 230 V, What are the number of turns in secondary if the voltage generated in secondary is 460 V? Vp = 230V             Np = 60 Vs = 460V              Ns = ?  = Ns = Np x Vs/ Vp = 20 x 460/ 230 = 40 turns A transformer input voltage is 230 V and the current is 20 A. What is the output voltage if the output current is 10A. Vp = 230V             Vs = ? Ip = 20A                 Is = 10A Vp x Ip = Vs x Is 230 x 20 = Vs x 10 230 x 20/10 = 460V

NATIONAL GRID

Increasing voltage for transmission increases the voltage and decreases the current High current causes heating and results in loss of energy. By increasing the voltage, current is lowered and energy loss is prevented so transmission is efficient. H x I²

STEP UP TRANSFORMER	STEP DOWN TRANSFORMER
Increase the voltage	Decrease the voltage
It has more turns in secondary than in primary.	It has more turns in primary than in secondary
Voltage in secondary is greater = Is x Ns ↑	Voltage in secondary is lower = Is x Ns ↓
Connected next to the power station to transmit high voltage to reduce the heating effects of current during transmission.	Connected to the power supply before it reaches homes to reduce the voltage to 230 V.

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KEY TERMS

Magnet – A magnet is a material or an object that produces a magnetic field. Magnet has two poles – North Pole and South Pole Magnetic Field Lines – The magnetic field lines are a visual tool used to represent magnetic fields. Field lines are from north pole to south pole. Induce Magnetism – When a piece of non-magnetized magnetic material touches or approaches the pole of a permanent magnet, it becomes a magnet in itself. North Pole – One end of the compass needle points in the North direction and is called the North Pole of the magnet South Pole – One end of the compass needle points in the South direction and is called the South Pole of the magnet. Solenoid – Solenoid is a coil of wire. Electromagnets – It is the solenoid wound around an iron core. Relay – A relay is an electric or electromechanical switch consisting of an electromagnet, an ammateur, a spring and a set of electrical contacts. Circuit Breaker – It is an electromagnet which magnetised with a large flow of current and attracts the switch towards itself turning off the current. Motor Effect – Motion as a result of current in a magnetic field is called the motor effect. Flemming Left Hand Rule – When a current passes through a coil placed in a magnetic field, the coil experiences a force and starts to rotate. The direction of force is given by left hand rule. Magnetic Flux density – Magnetic flux density (B) is defined as the force acting per unit of current per unit of length in a cable placed at right angles to the magnetic field. Split Ring Commutator – These are rings that allow the direct current to move in the opposite direction to maintain full rotation. Electromagnetic Induction – It is the production of voltage or electromotive force due to a change in the magnetic field. Generator Effect – Current is produced because of the motion of a conductor in the magnetic field. Mechanical energy is transformed to electrical energy. Transformer – It is the device which is used to increase (step up) or decrease the voltage (step down) or the potential difference. Step Up Transformer – It is the device which is used to increase (step up) or the potential difference. Step Down Transformer – It is the device which is used to decrease the voltage (step down) or the potential difference. Transformer Efficiency – Efficiency of a transformer can be defined as the output power divided by the input power. National Grid – Electricity is transferred from the power plant to consumers via the National Grid

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Disclaimer:

I have tried my level best to cover the maximum of your specification. But this is not the alternative to the textbook. You should cover the specification or the textbook thoroughly. This is the quick revision to help you cover the gist of everything. In case you spot any errors then do let us know and we will rectify it. References: BBC Bitesize Wikipedia Wikimedia Commons Image Source: Wikipedia Wikimedia Commons Flickr Pixabay