Circuits 4.0 / 5 based on 1 rating ? PhysicsElectricityGCSEWJEC Created by: Katy **Created on: 03-01-14 12:36 Current The effect. The flow of electrons around a circuit. Measured in Amperes (amps) - A. To meaure the ammeter is is series with the component (wire / bulb). 1 of 10 Voltage The drive. The push given to electrons. Measured in Volts - V To measure have the voltmeter in parallel with component. 2 of 10 Resistance Opposes the current. Measured in ohmns. Resistance = voltage/current Resistance of a wire: metal ions arranged in a lattice electrons pass through the metal → bump into positive ions no. of collisions = resistance of wire more collisions = higher resistance 3 of 10 Resistance & Current A bigger resistance = electrons find it harder to pass through the metal. This means there is less electrons flowing in the current. increase resistance = decrease current 4 of 10 Effecting Resistance Temperature: increase temperature = increase resistance paricle vibrate making it harder for electrons to pass through = more collisions Length: longer = increase resistance more ions = more collisions Thickness: thicker = decrease resistance more electrons = less collisions Material: depends on the number of free electrons 5 of 10 Current & Voltage Current & voltage can be proportional no gradient change = no resistance change Same increase in voltage: -smaller increase in current -increase resistance Wire at constant temperature: -resistance constant -increase voltage = increase current Lamp / heater (increase temperature): -increase voltage = increase current increase resistance 6 of 10 Variable resistor Used to vary the current passing through the resistor. Act as a voltage divider. Increase resistance of varible resistor: -increase total resitance → reduces current -increase resistors share of voltage → reduces voltage across 7 of 10 Electrical circuits at home conected in parallel Advantages: one stops working - others will carry on voltage is same for all components easier to connect up circuits & to add easy to work out total current drawn by parts of circiut safer - each part is protected by fuse / circiut breaker / switch 8 of 10 Series current is the same at any point in the circuit all components have the same current flowing through them 9 of 10 Parallel current splits when it gets to a junction in the circiut no current is lost at the juction total current in to the junction = total current out of the junction 10 of 10
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