# Electromagnetic induction

2.4.1 Magnetic ux
Magnetic ux is through a surface is the component of the magnetic B eld passing through that surface. It is de ned by the equation φ = AB cosθ
where φ is magnetic ux, A is the surface area of item being considered, B is the magnetic eld strength and θ is the angle to the normal to the surface.

2.4.4 Fleming’s right and left hand rules
(not to be confused with the right hand grip rule)

(for generators) We use Fleming’s left-hand rule to nd the direction of the force, eld or current from the other. The left-hand rule puts your thumb, rst nger and second nger perpendicular (at right angles) and makes the thumb the direction of the force, the rst nger the direction of the eld and the second nger the direction of the current. This rule is used when a magnetic eld induced by a current interacts with a magnetic eld from a magnet, in a generator where a current is induced by a magnetic eld, the same rule is applied but with the right-hand.

2.4.5 Alternating current and the root mean square (rms)
Alternating current (AC) is di erent from direct current (DC) in that the voltage is not constant (V = IR), so when we look AC circuits, we must nd the root mean square pd.

2.4.6 The oscilloscope
On an oscilloscope, the vertical axis is a volts per division (volts/div) axis and the horizontal axis is seconds per division (sec/div) axis. The division is set by a dial, i.e. each division (square) of our oscilloscope is one of a division set on a dial, the vertical axis is set on a volt/div dial and the horizontal is set on a

sec/div dial, both dials may be some multiple of that number too (i.e. milli, micro, etc). You can easily use this to work out values, simply treat it like any other graph, it’s just that the scale is controlled by the dial.