RESISTORS IN SERIES AND PARALLEL
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Resistors can be connected either in series or in parallel. When resistors are in series, the same current passes through each resistor and the total voltage equals the sum of the individual voltages across each resistor. The equivalent resistance of resistors in series is the sum of the individual resistances. When resistors are in parallel, the total current splits across the resistors and the equivalent resistance is lower than the lowest individual resistance.
RESISTORS IN SERIES AND PARALLEL
- 1. Resistors in series and parallel
- 2. Resistors in series • When two or more resistors are connected end to end, they are said to be in series. The resistors could be simple resistors or bulbs or heating elements or other devices • The three resistors R1, R2 and R3 connected in series. • The amount of charge passing through resistor R1 must also pass through resistors R2 and R3 since the charges cannot accumulate anywhere in the circuit
- 6. • Due to this reason, the current I passing through all the three resistors is the same. • According to Ohm’s law, if same current pass through different resistors of different values, then the potential difference across each resistor must be different • Let V1, V2 and V3 be the potential difference (voltage) across each of the resistors R1, R2 and R3 respectively, then we can write V1 = IR1, V2 = IR2 and V3 = IR3. • But the total voltage V is equal to the sum of voltages across each resistor
- 7. • where RS is the equivalent resistance • When several resistances are connected in series, the total or equivalent resistance is the sum of the individual resistances
- 10. Resistors in parallel • Resistors are in parallel when they are connected across the same potential difference • In this case, the total current I that leaves the battery is split into three separate paths. • Let I1, I2 and I3 be the current through the resistors R1, R2 and R3 respectively. • Due to the conservation of charge, total current in the circuit I is equal to sum of the currents through each of the three resistors.
- 14. • Since the voltage across each resistor is the same, applying Ohm’s law to each resistor, we have • Substituting these values in equation
- 15. • Here RP is the equivalent resistance of the parallel combination of the resistors. • Thus, when a number of resistors are connected in parallel, the sum of the reciprocal of the values of resistance of the individual resistor is equal to the reciprocal of the effective resistance of the combination
- 16. • The value of equivalent resistance in parallel connection will be lesser than each individual resistance. • House hold appliances are always connected in parallel so that even if one is switched off, the other devices could function properly.