Presentation on theme: "Series and Parallel Circuits"— Presentation transcript:
1 Series and Parallel Circuits Chapter 23Series and Parallel Circuits
2 Types of Circuit There are two types of electrical circuits; PARALLEL CIRCUITSSERIES CIRCUITS
3 SERIES CIRCUITSThe components are connected end-to-end, one after the other.They make a simple loop for the current to flow round.If one bulb ‘blows’ it breaks the whole circuit and all the bulbs go out.
4 PARALLEL CIRCUITS The components are connected side by side. The current has a choice of routes.If one bulb ‘blows’ there is still be a complete circuit to the other bulb so it stays alight.
5 Measuring CurrentElectric current is measured in amps (A) using an ammeter connected in series in the circuit.A
6 Measuring Current A A This is how we draw an ammeter in a circuit. PARALLEL CIRCUITSERIES CIRCUIT
7 Measuring Current SERIES CIRCUIT current is the same at all points in the circuit.2APARALLEL CIRCUIT2A2Acurrent is sharedbetween thecomponents1A1A
8 Measuring VoltageThe ‘electrical push’ which the cell gives to the current is called the voltage. It is measured in volts (V) on a voltmeterV
9 Measuring VoltageDifferent cells produce different voltages. The bigger the voltage supplied by the cell, the bigger the current.Unlike an ammeter a voltmeter is connected across the componentsScientist usually use the term Potential Difference (pd) when they talk about voltage.
10 Measuring Voltage V V This is how we draw a voltmeter in a circuit. SERIES CIRCUITPARALLEL CIRCUIT
11 Series CircuitVoltage is shared between the components3V1.5V1.5V
12 Parallel Circuit Voltage is the same in all parts of the circuit. 3V
13 Resistors in SeriesWhen two or more resistors are connected end-to-end, they are said to be in seriesThe current is the same in all resistors because any charge that flows through one resistor flows through the otherThe sum of the potential differences across the resistors is equal to the total potential difference across the combination
14 Resistors in Series, cont Potentials addΔV = IR1 + IR2 = I (R1+R2)Consequence of Conservation of EnergyThe equivalent resistance has the effect on the circuit as the original combination of resistors
15 Equivalent Resistance – Series Req = R1 + R2 + R3 + …The equivalent resistance of a series combination of resistors is the algebraic sum of the individual resistances and is always greater than any of the individual resistors
16 Equivalent Resistance – Series: An Example Four resistors are replaced with their equivalent resistance
17 Resistors in ParallelThe potential difference across each resistor is the same because each is connected directly across the battery terminalsThe current, I, that enters a point must be equal to the total current leaving that pointI = I1 + I2The currents are generally not the sameConsequence of Conservation of Charge
18 Equivalent Resistance – Parallel, Example Equivalent resistance replaces the two original resistancesHousehold circuits are wired so the electrical devices are connected in parallelCircuit breakers may be used in series with other circuit elements for safety purposes
19 Equivalent Resistance – Parallel The inverse of the equivalent resistance of two or more resistors connected in parallel is the algebraic sum of the inverses of the individual resistanceThe equivalent is always less than the smallest resistor in the group
21 Ground WireElectrical equipment manufacturers use electrical cords that have a third wire, called a case groundPrevents shocks
22 Ground Fault Interrupts (GFI) Special power outletsUsed in hazardous areasDesigned to protect people from electrical shockSenses currents (of about 5 mA or greater) leaking to groundShuts off the current when above this level