Thursday, February 18, 2010

Potential difference

Gravitational potential energy at x is greater than the gravitational potential energy at y.
The ball will fall from x to y when the apple is released. This due to the difference in the gravitational energy.
Electric current flows from a to b, passing the bulb in the circuit and lights up the bulb.
This is due to the electric potential difference between the two terminals.
As the charges flow from a to b, work is done when electrical energy is transformed to light and heat energy.

Potential difference: Work done to move 1 Coulomb of charge from one point to another in an electric field.

where V = potential difference [Volt]
E = energy released / work done [Joule]
Q = charge [Coulomb]

• Charges move from high potential to low potential, the moving charge called ”current”

• Potential difference can be measured with a voltmeter connected in parallel across two points within an electric circuit

Worked example :
1. If a charge of 5.0 C flows through a wire and the amount of electrical energy converted into heat is 2.5 J. Calculate the potential differences across the ends of the wire.

solution :

W = QV
2.5 = 5.0 (V)

V = 0.5 V