| A | B |
|---|
| symbol for magnetic field | B |
| units for magnetic field | tesla (T) |
| like poles | repel |
| unlike poles | attract |
| resistance R | = V/I |
| resistors in series | R1+R2+R3 |
| resistors in parallel | 1/R(total) = 1/R1 + 1/R2 |
| Power P | = E/t |
| Charge Q | = It |
| Energy E | = VIt |
| electrons travel | opposite to current |
| V(RMS) | = V(peak)/2^0.5 |
| V(p-p) | = 2 * V(peak) |
| right hand GRIP rule | gives direction of B from direction of current |
| right hand SLAP rule | gives direction of force from directions of field (B) and current (I) |
| Power (P) | = VI |
| Units of power | Watts (W) |
| Units of charge | Coulombs (C) |
| Potential Difference | is the same as Voltage |
| frequency (f) | = 1/T (period) |
| When B and I are parallel | there is zero magnetic force |
| torque | twisting effect of a force |
| rotor of an electric motor | armature |
| brushes | conects armature to voltage supply |
| commutator | reverses current in armature every half turn |
| commutator often works by | a SPLIT-ring arrangement |
| AC motors connect the voltage via: | SLIP-rings |
| electromagnet | magnet made by coil of current |
| solenoid | extended coil of wire |
| flux is measured in | webers (Wb) |
| formula for flux | phi = BA (B perpendicular to A) |
| Faradays Law | emf = -n (change in flux)/(change in time) |
| transformer action is | stepping up or down AC voltages |
| induced emf | voltage made when flux changes through a coil |
| transformer formula | N1/N2 = V1/V2 |
| for 'perfect' transformers | power in = power out |
| three formulae for power loss | P = VI = I^2R = V^2/R |
| high voltage transmission | can lower I and power loss |
| thicker wires | have less resistance |
| electrical safety concentrates on | keeping I through the body low |
| units of emf | volts |
| meaning of emf | voltage of a voltage SOURCE |
| stator | stationary coils (electromagnets)) |
| Lenz's Law | induced emf opposes CHANGE |
