A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω and a standard cell of emf 4V. A constant current flows through potentiometer wire. The length of the null point for cell of emf20 mV is found to be 60 cm. The resistance of the potentiometer wire is _____ Ω.
Correct Answer: 20
Solution and Explanation
\(l = 300 \;cm\)
\(ε = Kx\)
\(20 \times 10^{-3}\)
= \(\bigg(\frac{4 \times R}{780 + R} \times \frac{1}{300}\bigg)60\)
\(R = 20\)
Top Questions on Resistance
The graph between variation of resistance of a wire as a function of its diameter keeping other parameters like length and temperature constant is
- KCET - 2025
- Physics
- Resistance
- A current of 2 A flows through a conductor with a resistance of 5 \(\Omega\). Calculate the potential difference across the conductor.
- MHT CET - 2025
- Physics
- Resistance
- The S.I. unit of electrical resistance is
- TS POLYCET - 2024
- Physics
- Resistance
- Calculate the resultant resistance in the following circuit.
- TS POLYCET - 2024
- Physics
- Resistance
- Formula for specific resistance is
- TS POLYCET - 2024
- Physics
- Resistance
Questions Asked in JEE Main exam
The remainder when \( 64^{64} \) is divided by 7 is equal to:
- JEE Main - 2025
- Arithmetic Progression
- The sum of the infinite series $ \cot^{-1} \left( \frac{7}{4} \right) + \cot^{-1} \left( \frac{19}{4} \right) + \cot^{-1} \left( \frac{39}{4} \right) + \cot^{-1} \left( \frac{67}{4} \right) + ... $ is:
- JEE Main - 2025
- Sequence and series
- If $ \alpha $ is a root of the equation $ x^2 + x + 1 = 0 $ and $$ \sum_{k=1}^{n} \left( \alpha^k + \frac{1}{\alpha^k} \right)^2 = 20$$, then n is equal to _______
- JEE Main - 2025
- Sequence and series
x mg of Mg(OH)$_2$ (molar mass = 58) is required to be dissolved in 1.0 L of water to produce a pH of 10.0 at 298 K. The value of x is ____ mg. (Nearest integer) (Given: Mg(OH)$_2$ is assumed to dissociate completely in H$_2$O)
- JEE Main - 2025
- Equilibrium
- The amount of calcium oxide produced on heating 150 kg limestone (75% pure) is _______ kg. (Nearest integer)
Given: Molar mass (in g mol$^{-1}$) of Ca-40, O-16, C-12- JEE Main - 2025
- Stoichiometry and Stoichiometric Calculations
Concepts Used:
Resistance
Resistance is the measure of opposition applied by any object to the flow of electric current. A resistor is an electronic constituent that is used in the circuit with the purpose of offering that specific amount of resistance.
R=V/I
In this case,
v = Voltage across its ends
I = Current flowing through it
All materials resist current flow to some degree. They fall into one of two broad categories:
- Conductors: Materials that offer very little resistance where electrons can move easily. Examples: silver, copper, gold and aluminum.
- Insulators: Materials that present high resistance and restrict the flow of electrons. Examples: Rubber, paper, glass, wood and plastic.
Resistance measurements are normally taken to indicate the condition of a component or a circuit.
- The higher the resistance, the lower the current flow. If abnormally high, one possible cause (among many) could be damaged conductors due to burning or corrosion. All conductors give off some degree of heat, so overheating is an issue often associated with resistance.
- The lower the resistance, the higher the current flow. Possible causes: insulators damaged by moisture or overheating.