# Electric Potential

Unit 4 - AQA A

- Created by: Amy
- Created on: 07-01-13 13:24

First 304 words of the document:

PHY4A

Electric Potential and Charged Particle Acceleration

Electric Potential

If a charge is moved in an electric field, then work is done/energy is converted.

The potential V at a point in a field is the work done W per unit charge q in taking positive charge

from infinity to that point.

V = W

Q

Around a spherical conductor, carrying charge Q:

V = kQ

r

Where r is the distance of the point from the centre of the charge Q.

Note

V is a scalar quantity

The electric field strength is equal in magnitude to the potential gradient

Positive charges move down a potential gradient ( from high to low potential)

Negative charges move up a potential gradient (from high to low potential)

The relationship between V and distance is inversely proportional

Equipotential surfaces

Points that are at the same potential lie on equipotential surfaces. Around a spherical charge, these

are concentric spheres or circles in two dimensions. Equipotential surfaces are always perpendicular

to field lines.

Motion of charges particles

Acceleration

The idea of potential can be used to describe the acceleration of charged particles. It follows from

the definition of the volt that the kinetic energy gained by a particle carrying a charge q when

accelerated through a potential difference of V volts is given by:

1 mv² = QV

2

Where m is the mass of the particle and v is its subsequent speed.

This equation can be used to calculate the speed of an electron as it emerges from an electron gunm

as used in televisions. The deflection of these electrons across the screen is also caused by electric

fields.

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