4. Charges in an atom -ve electrons +ve nucleus In a neutral atom, the number of positive charges in the nucleus equals the number of negative electrons orbiting it
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8. Controlling a circuit by breaking it -ve +ve Conductor: The most suitable, domestically, is copper. Silver is best, but too expensive. Aluminium is used in overhead cables because it is light. -ve +ve Circuit closed, current flows Circuit broken, no current switch
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12. All use rotating generators Hydro power Nuclear power Tidal power Wind power
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16. AC power supply in principle Live wire: voltage change from -240V to +240 volts Neutral wire: voltage constant at 0 volts Current alternates direction 50 times per second, 50Herz When an electrical unit hums, it does so at a tone of 50Herz