# Electromagnetism

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# Topics covered

• appreciate that there is a force on a charged particle when it moves in a magnetic field as long as its motion is not parallel to the field
• recall that a force is exerted on a current-carrying wire in a magnetic field, and how this effect is applied in simple d.c.electric motors and loudspeakers
• use the left hand rule to predict the direction of the resulting force when a wire carries a current perpendicular to a magnetic field
• recall that the force on a current-carrying conductor in a magnetic field increases with teh strength of the field and with the current
• electromagnetic induction
• recall that a voltage is induced in a conductor or a coil when it moves through a magnetic field or when a magnetic field changes though it; recall the factors which affect the size of the induced voltage
• describe the generation of electricity by the rotation of magnet within a coil of wire and a coil of wire within a magnetic field; describe the factors which affect the size of the induced voltage
• recall the structure of a transformer and understand that a transformer changes the size of an alternating voltage by having different numbers of turns on the input and output sides
• explain the use of step-up and step-down transformers in the large-scale generation and transmission of electrical energy
• recall and use the relationship between input(primary) and output(secondary) voltages and the turns ratio for a transformer: Primary voltage/secondary voltage = primary turns/secondary turns
• input power = output power for 100% efficiency