5.1+ELECTRIC+POTENTIAL+DIFFERENCE,+CURRENT+AND+RESISTANCE

Back to ELECTRIC CURRENTS 5.1 ELECTRIC POTENTIAL DIFFERENCE, CURRENT AND RESISTANCE 5.2 ELECTRIC CIRCUITS
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ELECTRIC POTENTIAL DIFFERENCE, CURRENT AND RESISTANCE
ELECTRIC CHARGE (Q): The cause of electric fields and currents. Either positive or negative. Q=It THE COULOMB (1C): The charge which passes a point when 1 A flows for 1s. 1C = 6.25 x 10 18 electronic charges. e = 1.60 x 10 –19 C

FROM THE DATABOOK:

ELECTRIC POTENTIAL ENERGY (W): The energy gained when work is done moving a charge in an electric field.

Define //electric potential difference//. ELECTRIC POTENTIAL DIFFERENCE (V): The work done per unit charge moving a positive test charge between two points in a circuit. V=W/Q measured in volts.

A PD acts across a component.

VOLT (1V): Unit of PD. One joule of electric potential energy is transferred to other forms when one coulomb flows between two points.

Determine the change in potential energy when a charge moves between two points at different potentials.

Define the //electronvolt//. ELECTRONVOLT: Unit of energy. The energy required to move one electron through a PD of one volt. W (eV) = q (electron charges) x V (volts)

Solve problems involving electric potential difference.

Define //electric current//. ELECTRIC CURRENT (I): The rate of flow of charge. Unit is the ampere. Conventional current flows from + to –

A current flows through a component.

It is sufficient for students to know that current is defined in terms of the force per unit length between parallel current-carrying conductors.

[|HOW CURRENT WORKS IN SOME MATERIALS] simulation showing the concept of positive charge as 'holes'

Define //resistance//. RESISTANCE (R): The ratio of PD across a conductor to current through the conductor.

THE OHM (1Ω): 1Ω = 1V/A (HINT: Ω is alt-z on the Mac keyboard) Students should be aware that //R// = //V/////I// is a general definition of resistance. It is not a statement of Ohm’s law. Students should understand what is meant by resistor media type="custom" key="25199942"

Apply the equation for resistance in the form

where //ρ// is the resistivity of the material of the resistor State Ohm’s law

OHM’S LAW: The current through a conductor is directly proportional to the voltage across its ends if the temperature and other conditions are constant.

IB DCP PRACTICAL ON V-I CHARACTERISTICS See the above page for a link to advice about drawing graphs. Or click here.

Compare ohmic and non-ohmic behaviour.

NON-OHMIC CONDUCTOR: A conductor which does not obey Ohm’s Law ie V is not proportional to I.

[|2 IB PAPER 2 Q1 ON RESISTANCE] - practice your data analysis skills [|MARKSCHEME FOR THE ABOVE]

Derive and apply expressions for electrical power dissipation in resistors. POWER (P): The rate of converting energy. Unit is watt (W) = 1J/S



Solve problems involving potential difference, current and resistance.