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If the RC firing circuit used for firing an SCR is to be used to fire a TRIAC then

If the RC firing circuit used for firing an SCR is to be used to fire a TRIAC then Correct Answer the diode should be replaced by a diac

The TRIAC is a bidirectional SCR, hence it will need gating in both the directions. This can be achieved by replacing the diode by a DIAC (bidirectional diode).

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