A pair of carbon brushes
Diagram of a spark transmitter
A typical SCR based light dimmer which dims the light through phase angle control. This unit is wired in series with the load. Diodes (D2, D3, D4 and D5) for a bridge which generates DC with much ripple. R and C form a circuit with a time constant, as the voltage increases from zero (at the start of every halfwave) C will charge up, when C is able to make ZD conduct and inject current into the SCR the SCR will fire. When the SCR conducts then D1 will discharge C via the SCR. The SCR will shut off when the current falls to zero when the supply voltage drops at the end of the half cycle, ready for the circuit to start work on the next half cycle.

Electrical contact which conducts current between stationary wires and moving parts, most commonly in a rotating shaft.

- Brush (electric)

Electric motors that have a commutator can suffer from sparking at the brushes.

- Television interference
A pair of carbon brushes

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