Sure! Let's go through each question step by step, providing brief explanations after each step, and then give the final answer. --- ### Q13 **Step 1:** In an RL circuit, the time-variation of voltage across the resistor depends on the current, which changes with a characteristic time constant. - *Explanation:* The time constant for an RL circuit is \( \tau = \frac{L}{R} \). **Step 2:** The answer must involve L/R. - *Final Answer:* **a) L/R only** --- ### Q14 **Step 1:** Inductance depends on the geometry (length, area, number of turns) of a coil. - *Explanation:* Inductance is not dependent on frequency, but on the physical setup. **Step 2:** The answer is geometry. - *Final Answer:* **b) geometry** --- ### Q15 **Step 1:** A constant magnetic field does not induce an electric field. - *Explanation:* Only a *changing* magnetic field induces an electric field. **Step 2:** The answer is none of these. - *Final Answer:* **D) None of these.** --- ### Q16 **Step 1:** An iron core increases the magnetic field in a solenoid by aligning its magnetic domains. - *Explanation:* The iron core's domains align with the external field, increasing total flux. **Step 2:** The answer is alignment of domains within iron core. - *Final Answer:* **A) The alignment of magnetic domains within the iron core.** --- ### Q17 **Step 1:** According to Faraday's Law, a changing magnetic flux induces an opposing EMF. - *Explanation:* The coil generates an opposing magnetic field. **Step 2:** The answer is that the coil generates a magnetic field in the opposite direction. - *Final Answer:* **A) The coil generates a magnetic field in the opposite direction.** --- ### Q18 **Step 1:** At full speed, the back EMF in the motor is highest, reducing current draw. - *Explanation:* Increased back EMF opposes the supply voltage, lowering current. **Step 2:** The answer is the increase in back EMF reduces current. - *Final Answer:* **B) The increase in back-EMF reduces the effective voltage, lowering current.** --- ### Q19 **Step 1:** Faraday's law applies when a moving magnet changes flux through a coil. - *Explanation:* Changing magnetic flux through a coil induces EMF. **Step 2:** The answer is coil. - *Final Answer:* **a) a coil** --- ### Q20 **Step 1:** In empty space, a changing electric field induces a magnetic field. - *Explanation:* Maxwell's equations state that a time-varying electric field creates a magnetic field. **Step 2:** The answer is a changing electric field. - *Final Answer:* **B) a changing electric field** --- ### Q21 **Step 1:** The induced electric field is always perpendicular to the changing magnetic field. - *Explanation:* By Faraday's Law, the induced electric field forms closed loops perpendicular to the changing magnetic field. **Step 2:** The answer is perpendicular. - *Final Answer:* **c) perpendicular to the changing magnetic field** --- ### Q22 **Step 1:** Moving copper over a magnet induces currents (eddy currents), temporarily magnetizing the copper. - *Explanation:* Copper becomes a temporary magnet when moved relative to a magnet. **Step 2:** The answer is copper is turned into a temporary magnet. - *Final Answer:* **A) copper is turned into a temporary magnet** --- ### Q23 **Step 1:** The EMF field is non-conservative, its closed path integral is not zero, and work depends on the path, not just initial/final positions. - *Explanation:* All listed statements are correct. **Step 2:** The answer is all of these. - *Final Answer:* **D) All of these** --- Let me know if you need further breakdown or explanations for any specific question!