Unit 2 - Electromagnetism Flashcards
what is the ‘electric field strength at a point’
The electrostatic force on one coloumb of charge placed at a point
What is ‘E’ measured in (electric field strength)
N C ^-1
what direction do electric fields point in
From positive to negative
What is ‘electrostatic potential at a point’
the work done to bring one coloumb of charge from infinity to that point.
What is the gravitational potential at a point?
The work done in moving a unit mass from infinity to that point in a field.
What is an electric field
The region that surrounds electrically charged particles in which a force is extenúes on other electrically charged particles
Explain how the results of Millikans experiment lead to the idea of quantisation of charge.
Millikan determined the charge of a number of smaller charged droplets, He notices that all the charged were multiples of a certain small charge - 1.6x10^-19 This suggested that it was not possible to obtain a charge with a fraction of this value.
Name the forces on an oil droplet in millikans experiment
upwards - electrostatic force
downwards - weight if the drop
What is an equipotential surface?
Equipotential surfaces have the same potential at all points. Moving a charge between 2 points on an equipotential surface needs no work.
State the condition for a magnetic field to exist
a magnetic field is produced around MOVING charges
What is a tesla
one tesla is the magnetic induction of a magnetic field which q conductor of length one metre, carrying a current of one ampere perpendicular to the field is acted on by a force of one newton.
What is electric field strength?
Force acting per unit positive charge
When ions in a uniform electric field have a smaller velocity than expected they follow a curved path, why?
Since F=qvB, at lower speeds the magnetic force is reduced therefore there is an unbalanced force downwards - magnetic force < electric force.
