Test on Electronic components: diode, LED, transistor, capacitor

Question 1: A capacitor stores electrical energy primarily in a magnetic field within its dielectric material.

A. Yes

B. No

Explanation: The study material states that a capacitor stores electrical energy in an electric field, not a magnetic field, within its dielectric.

Question 2: According to the provided study materials, what describes the current-voltage relationship for a capacitor?

A. The current through a capacitor is directly proportional to the voltage across it.

B. A capacitor allows current to flow only when the voltage across it is changing.

C. If the voltage across a capacitor is constant (DC), it acts as a short circuit once fully charged.

D. The current (I) through a capacitor is proportional to the rate of change of voltage (dV/dt) across it.

Explanation: The study materials state: 'The current (I) through a capacitor is proportional to the rate of change of voltage (dV/dt) across it: I = C · dV/dt.' This directly matches option 3. Furthermore, the text explains: 'This means a capacitor allows current to flow only when the voltage across it is changing,' which matches option 1. Option 0 is incorrect as the current is proportional to the *rate of change* of voltage, not the voltage itself. Option 2 is incorrect because the text states, 'If the voltage is constant (DC), the capacitor acts as an open circuit once fully charged,' not a short circuit.

Question 3: Capacitors are used in decoupling to stabilize power supplies by providing local energy storage.

A. Yes

B. No

Explanation: Capacitors are indeed used in decoupling to stabilize power supplies by providing local energy storage, as stated in the 'Typical Applications' section of the study materials.

Question 4: In a simulation observing a charged capacitor discharging through a resistor, which of the following statements accurately describes what a student would observe regarding its behavior?

A. Increasing the resistance (R) or capacitance (C) would shorten the capacitor's discharge time.

B. The voltage across the capacitor would decrease exponentially, approaching zero during discharge.

C. The time constant (τ) would remain unaffected by changes in R or C during discharge.

D. Varying either R or C would directly change how quickly the capacitor discharges.

Explanation: When a charged capacitor discharges through a resistor, its voltage decreases exponentially. In a simulation, observing the voltage across the capacitor over time will show the characteristic exponential curve, approaching zero during discharging. The time constant (τ) directly affects how quickly the capacitor discharges, and it changes by varying the resistance or capacitance. Increasing R or C will lengthen the discharging time, not shorten it.

Question 5: When the reverse voltage across a diode exceeds the breakdown voltage (V_BR), the diode's junction operates without risk of damage.

A. Yes

B. No

Explanation: If the reverse voltage increases beyond the breakdown voltage (V_BR), the diode's junction can be damaged, leading to a sudden increase in reverse current.