Physics · Current Electricity · NEET
The CURRENT is the same through every resistor because there is only one path, so the same charge per second passes through each. The VOLTAGE is NOT the same; the total voltage of the battery splits between the resistors (V = V1 + V2 + V3). Confusing these two is the number one series mistake in NEET.
Adding a resistor in series adds one more obstacle in the single path, so it always makes it harder for current to flow. Since R_series = R1 + R2 + R3, the sum must be greater than any one term. Quick check: if your series answer is smaller than the biggest resistor, you have made an error (that only happens in parallel).
Same current I flows through all three. The drops are V1 = IR1, V2 = IR2, V3 = IR3. The battery voltage equals their sum: V = V1 + V2 + V3 = I(R1 + R2 + R3). Replacing the three with one resistor R_series that carries the same I and same V gives V = I R_series, so R_series = R1 + R2 + R3.
The LARGEST resistor drops the most voltage. Because current I is the same for all, V = IR means the drop is directly proportional to R. So a 6 ohm resistor drops twice the voltage of a 3 ohm resistor in the same series loop. This ratio idea is tested often.
The effective resistance of four identical wires in parallel is 0.25 ohm. Their effective resistance in series is:
10 resistors (R each) in series with a battery (emf E, negligible internal resistance) are then reconnected in parallel; the current increases n times. The value of n is:
A wire of resistance 100 ohm is divided into 10 equal parts. The first 5 are connected in series, the next 5 in parallel; the two combinations are then in series. The resistance of the final combination is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
R_series = R1 + R2 + R3 + ... You simply add all the resistances. The equivalent resistance is always greater than the largest individual resistor.
Yes. Because there is only one path, the same current I flows through every resistor and every point of a series circuit.
The battery voltage divides in proportion to resistance: V1:V2:V3 = R1:R2:R3, since V = IR and I is common. The bigger resistor takes the bigger share.
Use series when the components lie on a single line with no branching, so the same current passes through all of them. If the current splits into branches, it is parallel.
It increases the total resistance, which decreases the current drawn from the battery (I = V / R_series).
