Topic 5: Electric Potential Difference, Current and Resistance

² Electric potential difference: work done per unit charge to move a positive test charge between A and B. ² Joule / coulomb = Volt

² The change in the electrical potential energy = the work done ² Moving from point A (low EP) to point B (high EP)makes charge q gain electrical potential energy ² △potential energy = F * d = E * q * d

² The energy acquired by an electron as it moves through a potential difference of 1 volt. ² 1 eV = 1.6 x 10^-19­J

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² The flow of charged particles through a material when a potential difference is applied across it. ² Rate of flow of charge ² Unit: Ampere (A) ² Conventional <-> electron flow

² a measure of how difficult a charge can flow in a material ² Unit: Ohms (Ω) R = V/I

² Provided that the physical conditions such as temperature are kept constant, the resistance is constant over a wide range of applied potential differences and therefore the potential difference is directly proportional to the current. ² potential difference α current. ² Voltage = Current * Resistance

² In ohmic behavior, V and I are proportional to each other. ² In non-ohmic behavior, V and I are not proportional to each other.

² Electrical power is the rate that an electrical device uses energy. P = E/t = I²R = V²/R

² The amount of energy per unit charge supplied to a circuit by a power source.

resistance inside a battery that causes the battery's terminal potential difference to be less than its emf

See pic

Ammeter: ² Measure Current ² In series ² Minimum Resistance ² Ideal ammeter -> 0 Ω Voltmeter: ² Measure voltage ² In parallel ² Maximum Resistnace ² Ideal Voltmeter -> ∞ Ω

two resistors placed in series that divide up the battery's potential difference

Resistance is decreased depending on the amount of light shining on its surface/temperature/change in length so
1. Light stops shining on LDR 2. Resistance increase 3. Potential difference increase 4. Light on!