Electronics 0.0 / 5 ? PhysicsD.C. ElectricityElectric fieldsASAQA Created by: Vickid1017Created on: 04-04-18 11:15 Power Power is the rate of energy transfer, in joules per second (j/s) or watt (W). 1 of 16 Energy Electrical energy is often measured in kWh 1kWh = 3.6 x 10^6 J 2 of 16 Efficiency The efficiency of an electrical device is the % of electrical energy (or power) input that's transferred usefully. 3 of 16 Charge Charge, Q, is a property of matter, carried by charged particles, such as the electron and proton. Charge is measured in coulombs (C). The charge carried by an electron is -1.6 x 10^-19 C. 4 of 16 Current Current, I, is the rate of the flow of charge. Current= change in charge/ change in time I= Q/ t It's measured in amperes or amps (A). 5 of 16 Conventional Current The direction of conventional current is that in which positive charges flow from positive (+) to negative (-). 6 of 16 Conservation of Charge Charge is conserved in a circuit- the total current entering any point in a circuit equals the total current leaving that point. 7 of 16 Potential Difference The potential difference, V, between 2 points in a circuit is defined as the work done per unit charge passing between the points. V= W/ Q 8 of 16 Potential Difference Potential difference is measured using a voltmeter connected in parallel with the component. 9 of 16 Emf Around any closed loop of circuit, the sum of the emf is provided by power sources is equal to the sum of pd's across the components. 10 of 16 Electrical Power Power = current x voltage P= IV Power (W) Current (A) Voltage (V) 11 of 16 Energy Transferred The energy transferred, E, in a time, t, is: Energy transferred = current x voltage x time E= IVt 12 of 16 Resistance Resistance, R, is a measure of an electrical components opposition to current. Resistance = voltage/ current R= V/ I 13 of 16 Heat As a current passes through a resistor, energy is transferred as heat. 14 of 16 Ohm's Law Ohm's Law holds for metal conductors provided the temperature and other physical conditions are constant. The current through a component is proportional to the potential difference across it. 15 of 16 Resistivity The resistivity of a material of length, l, resistance, R, and cross-sectional area, A, is: p= RA/ L It's measured in Ω⋅m 16 of 16

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