Finding the Internal Resistance of a Power Pack

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Finding the Internal Resistance of a Power Pack

Aim

Design and Carry Out an experiment to determine the EMF and Internal

Resistance of a standard laboratory power pack.

Theory

This information was taken from the Collins advanced science Physics

textbook, the Cambridge Advance Science Physics 1 textbook and from

notes taken in class.

E.M.F or Electro Motive Force is the opposite of potential difference,

in that; it is the situation where a voltage is gaining energy. This

seems unlikely, but it is required in order to allow an electric

circuit to function. An electric current is a flow of electric charge,

the charge flows around the circuit, transferring some of its energy

to areas of resistance along the way (resistors, filament lamps,

buzzers). At some point along the way the energy must be initially

supplied, otherwise the whole process couldn't function. At the

beginning of the process the power supply provides the charge with

energy to pass to the circuit. This is the electro-motive force. EMF

is a type of voltage along with potential difference and these are

defined as:

A Voltage where the charge is losing energy is a potential difference,

V.

A Voltage where the charge is gaining energy is an electromotive force,

E.

A relationship exists between volts and joules. A 10v power supply,

for example, will give 10J of energy to each coulomb that it pushes

round the circuit. When a single coulomb passes through a component

with a p.d. of 5v, it transfers 5J of energy to the p.d. In it's

simplest form when 1C passes through a p.d. of 1v, it transfers 1v of

energy.

Power Supply

Resistor

[IMAGE]My investigation is concerned with the insides of the power

supply, commonly a power pack is made up of many wires, and a cell

contains chemical electrolytes and electrodes, both however work to

the same effect. When the charge passes through the source of e.m.f it

gains lots of energy, but also instantly loses some of that that it

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