# Physics P5

## Types of Charge/Van de Graaff Generators

• Protons -> +
• Neutrons -> 0
• Electrons -> -

When you rub objects together the electrons move from one to another

Robert J. Van de Graaff (1901-1967) and his generator

In 1929, American physicist Robert J. Van de Graaff invented his own generator. A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high electrostatic voltages on a hollow metal globe on the top of a stand.

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## Generators

Generators use movement (kinetic energy) to create electrical energy, using a process called electromagnetic induction.

How to increase current

• more wire (coils)
• stronger magnets
• increased movement

How to swap the current

• more wire in opposite direction
• swap magnets around
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## Generators 2

How to get a brighter bulb

• more coils
• faster
• atronger magnet

Dynamo - an electric generator, especially for direct current (short for dynamoelectric)

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## Voltmeters and Potential Difference/Resistance

• A voltmeter reads a more accurate potential difference than the front of the power supply
• A high potential difference results in a higher current
• High voltage -> brighter bulb

Resistance Equation

Resistance = potential difference / current

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## Series and Parallel Circuits

Series circuits havo on component after another, ammeters have to be in series to work properly

Parallel circuits involve multiple paths for the current to flow down (before returning to the power supply). Voltmeters have to be connected in parallel to work

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## Energy and Power

1 Watt = 1 Joule of energy per second

Energy Equation

Energy (J) = Power (W) x Time (s)

Power Equation

Power (W) = Voltage (V) x Current (A)

Mains voltage = 230V

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## Right- and Left-hand Rules

Right-hand rule (thumbs up with the right hand)

Thumb -> current

Fingers -> magnetic field lines

Left-hand rules (thumb up, fore finger pointing, middle finger 90 degrees)

Thumb -> movement

First -> field

Second -> current

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## Transformers

Transformer Equation

Voltage of primary / Voltage of secondary = No. of primary coils / No. of secondary coils

Vp / Vs = Cp / Cs

Vp x Cs = Vs x Cp

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## Transformers

Transformer Equation

Voltage of primary / Voltage of secondary = No. of primary coils / No. of secondary coils

Vp / Vs = Cp / Cs

Vp x Cs = Vs x Cp

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