Circuits — Set 4
Physics · परिपथ · Questions 31–40 of 50
Which relation expresses Ohm’s law for a conductor at constant temperature?
Correct Answer: C. V = IR
Ohm’s law states that voltage across a conductor is proportional to current, giving V = IR. Here R is the constant resistance for that conductor at a fixed temperature. The V-I graph is a straight line through the origin for an ohmic conductor.
What is the SI unit of electrical resistance?
Correct Answer: C. Ohm
Electrical resistance is measured in ohm, written as Ω. From V = IR, one ohm means 1 V produces 1 A. Resistances can be combined in series and parallel to get an equivalent value.
Kirchhoff’s current law is also known as which rule?
Correct Answer: A. Junction rule
Kirchhoff’s current law is called the junction rule because it applies at a node. It states that currents entering and leaving a junction balance. It is based on the idea that charge does not accumulate at a junction in steady state.
Kirchhoff’s voltage law is also known as which rule?
Correct Answer: B. Loop rule
Kirchhoff’s voltage law is called the loop rule because it applies to a closed loop. It states that the algebraic sum of potential changes around the loop is zero. It helps relate emfs and drops across elements in a circuit.
For resistors connected in series, how is the equivalent resistance expressed?
Correct Answer: C. Req = R1 + R2 + ...
In series, resistances add directly, so Req = R1 + R2 + ... . The same current flows through all series resistors. Adding more resistors in series increases total resistance.
For resistors connected in parallel, how is the equivalent resistance expressed?
Correct Answer: A. 1/Req = 1/R1 + 1/R2 + ...
In parallel, conductances add, so 1/Req = 1/R1 + 1/R2 + ... . Each branch has the same voltage but different current can flow. Adding a parallel branch decreases the equivalent resistance.
Which expression gives electrical power dissipated in a resistor when current I flows through it?
Correct Answer: D. P = I^2R
Power dissipated in a resistor is P = I^2R when current I flows through it. This power appears mainly as heat due to collisions of charge carriers. An equivalent form is P = V^2/R when the voltage across the resistor is known.
Which expression gives electrical energy consumed by a device operating at voltage V with current I for time t?
Correct Answer: B. E = VIt
Electrical energy consumed is E = VIt when a device runs at voltage V and current I for time t. This follows because power is P = VI and energy is E = Pt. Energy in household use is often measured in kWh.
Which symbol is commonly used to represent electrical resistivity?
Correct Answer: B. ρ
Resistivity is commonly represented by the Greek letter rho, ρ. It relates to resistance by R = ρL/A for a uniform conductor. The reciprocal of resistivity is conductivity, often written as σ.
What is the SI unit of conductance?
Correct Answer: B. Siemens
Conductance is measured in siemens, written as S. Conductance is the reciprocal of resistance, so G = 1/R. A higher conductance means a circuit allows current more easily.