8/14/2019 Physics - Summaries - Electromagnetism

1/5

Topicl0: ElectromagnetismMaPnetic fields due to currents

lons straisht conductins wire Flat circular coil

Solenoid

Note that direction of B-field is always out of North and into South -exceptwithin a bar magnet /solenoid. Within a bar magnet / solenoid, the direction ofthe B-field is from South to North!

When viewed from the bottom:

llPaee

8/14/2019 Physics - Summaries - Electromagnetism

2/5

Force on a current-carrying conductor

Any current-carrying conductor which is placed in a magnetic fieldlong as the current direction is not parallel to the field dirCclion.Examples:

will experience a force as

r&

Direction of torce can be determined by Fleminq's Left Hand RuleMagnitude offorce can be determined by equation:

Note: To determine 8"!, you have to resolve the B field into 2 components (tf djrection of B isnot already perpendicular to the conductor):(1) along the conductor, and12) perpendicularto the conductor-this is the 8,we want.

gcss!!-qab.!!e

2lPaee

To maintain the equilibrium of the wire frame, the P.inciples of Moments should be appliedto determine the unknown quantity.Sum ofanticlockwise moments = Som of clockwise moments (about pivot at Xy)

F>

8/14/2019 Physics - Summaries - Electromagnetism

3/5

Force adine on a charge movinq in a masnetic field

Step 1: Determine the current due to the motion ofthe charge. if charge is positive, current is ln direction of motion;. if charge is negative, current is in direction opposite to that of motion!!Cp.Z: Using Fleming's Left Hand Rule to determine the direction ofthe force acting on thecharge. {Maenitude ofthe force can be found using Fs : 6qu)

{

Step 3: ll you are asked to sketch the subsequent movement of the charges, note that as longas it remains within the uniform magnetic field, it will move in a circular oath.Direction of circular path is between directions of FB and v.

Force between 2 current-carving conductors

Currents in same direction. wires experience

attraction towardseach other

Currents in opoosite directions. wires experience repulsion

from each other

'.4..

3lPase

8/14/2019 Physics - Summaries - Electromagnetism

4/5

lf the scenario is such that the B-fields or 2 or more current-carrving conductors act on anothercurrent-carrying conductor, you willhave to:

(1) considerthe resultant B field at the site ofthe conductoryou are interested in;(2) then use Fleming's Left Hand Rule-Note: the B-field due to the conductor you're interested in should not be qq!5idered,ExamBle B-field due to Z

Resultant 8-field at XB-fild due toY

UJ,' Resultant force on X

Force by Z on X

Y& @

4lPace

8/14/2019 Physics - Summaries - Electromagnetism

5/5

5lPage