Do nowDo now::

An AC generator produces a peak voltage of 6V.It is connected to a heater which has 30Ω resistance.

a)Calculate the peak current and RMS current

b)Calculate the RMS power

c)What DC voltage would the heater need to work just as well as on the AC voltage?

Thursday, April 20, 2023

In pairs, discuss:In pairs, discuss:

What happens to the bulb in the AC circuit What happens to the bulb in the AC circuit compared to the DC circuit? compared to the DC circuit?

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In a In a DC DC circuit, the current flows until the cap is fully circuit, the current flows until the cap is fully charged and then stops.charged and then stops.

In an In an AC AC circuit, the current can continue to flow, as the circuit, the current can continue to flow, as the plates become alternately charged positively and plates become alternately charged positively and negatively negatively

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ReactanceReactance

For both AC and DC circuits, the voltage For both AC and DC circuits, the voltage across the resistor is related to the current across the resistor is related to the current by V=IRby V=IRA similar relationship exists for a capacitor:A similar relationship exists for a capacitor:

Where XWhere Xcc is the is the reactancereactance of the capacitor of the capacitor

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cc IXV

ReactanceReactance

Reactance is a measure of how a Reactance is a measure of how a capacitor can limit alternating currentcapacitor can limit alternating current

Unit: OhmsUnit: Ohms

It is It is similarsimilar to resistance but differs in that to resistance but differs in that it is dependent on the it is dependent on the frequencyfrequency of the ac of the ac supply.supply.

It also depends on the size of the It also depends on the size of the capacitor.capacitor.

ReactanceReactance

Explanations:Explanations:

Higher f means cap never gets full before Higher f means cap never gets full before current direction changes, so never limits current direction changes, so never limits current, so low Xcurrent, so low X

Higher C means that it takes more charge to fill Higher C means that it takes more charge to fill it, so never fills before current direction changes, it, so never fills before current direction changes, so never limits current, so low Xso never limits current, so low X

fCX c 2

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