GCSE PHYSICS - Electricity - How do Switches control Lamps in a Series Circuit? - What happens to the Brightness when extra Lamps are added in a Series Circuit?

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How does a Switch control Lamps in a Series Circuit?

A switch is said to be open when it is off
and closed when it is on. The circuit below shows
six lamps in a series circuit with an open switch.

An open switch in a series circuit turns everything off,
because the circuit is disconnected from the cell.

Lights in a Series Circuit

What happens to the Brightness
when extra Lamps are added in a Series Circuit?

When the switch in the circuit above is closed
(turned on) all of the lamps will light. When lamps
are connected in series, adding extra lamps in
the circuit makes them all go dimmer because the
total resistance of the circuit increases with each
extra lamp. A bigger resistance makes the current
decrease. A smaller current makes the lamps
become less hot and therefore shine less brightly.

The supply voltage is shared between all of the lamps.
Adding extra lamps decreases the voltage across
each individual lamp and so each lamp has less energy.

If one lamp in a series circuit breaks or fails, it
acts like an open switch and all the other lamps
will go out. For this reason, lights in a house
are always connected in parallel. The exception is
Christmas tree lights or fairy lights, where the
large mains voltage is shared between the lamps.

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