# Physics note P1A part 1

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• Created by: ok
• Created on: 19-05-11 21:34

Physics notes

Direct Current
Flows in one direction only usually in batteries.
Non rechargeable dry cell batteries are more popular than rechargeable batteries as they are used in more things.
Dry cell batteries are made by chemical reactions that happen in the cell.
There can be cells with Direct current where no chemical reaction happens such as solar cells. In Solar cells, the energy from the sun creates an electrical current.

Alternating Current flows in all direction.
Used in mains electricity and in dynamo. Stops the light bulbs from flickering

Conventional current is when the current flows from positive to negative.
However, if you look closely electrons are flowing in a negative to positive current, this is an electrical current.

Ammeter measures electrical currents in  amps. This is a measurement of the number of electrons passing each second. An ammeter is placed in series  of circuit. When smaller than an Amp it is measured in Milli amps which is one thousandth of an Amp.

V(Volts)=I(Current) x R (Resistance)
Battery rating in amp hours / Current used in amps = Time in hours

Volt is the 'electrical push' in a circuit. It is measured by a voltmeter in parallel in a circuit and is measured in volts/millivolts
Current is the flow of electricity in a circuit. It is measured by a voltmeter in series of a circuit measured in volts/millivolts.
Resistance is the measurement of conducting electricity. The more components in a circuit the more difficult it is for the current to flow. Resistance is measured in Ohms. Air has very high resistance and so does not conduct electricity, however in thunderstorms the voltage is so high that air reacts and conducts.
Graphs of currents In a graph there is pattern between the voltage and current. When the voltage increases the current does too. It is always a straight line diagonal upwards. Also, the higher the resistance the shallower the