Thursday, 21 April 2011

Quantities And Units (part-2)

c) Voltage (V)

1. Voltage is the potential energy that causes the current to flow in a circuit.
2. This potential energy is produced from a battery or a generator- electromotive fore (emf)
3. The current flows from a higher pressure ( + ) to a lower pressure point ( - ).
4. The unit for the potential difference and emf is volt (V).
5. Formula:

V = I X R

d) Resistance (R)

1. Resistance is a quantity that limit the flow of a current in a circuit.
2. The important characteristic is characteristic is  : low resistance in a circuit allows high current flow, 
    however if the resistance is high the current flow in the circuit will reduced or will become zero.
3. A good conductor = a very low resistance and a good insulator = a very high resistance.
4 Formula

R = V/I

e) Power (P)

1. Power is the rate at which energy is used.
2. A watt is unit for power.
3. Formula :

P = W/T

f) Energy (E)

1. Energy is the capability to do work in a tome.
2. Energy is measured in joule. One joule is equivalent to one watt in one second.
3. Formula :

W = V X I

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