elecs capacitor

A capacitor is connected to a DC source and fully charged. If the plate separation is suddenly doubled while still connected to the battery, what happens to the stored energy?

Decreases

Two capacitors, C1 = 4 µF and C2 = 8 µF, are connected in series to 12 V. Which statement is TRUE?

Both capacitors store the same charge

A capacitor is charged and then disconnected from the source. If the dielectric constant increases, what happens to the voltage across it?

Decreases

The energy stored in a capacitor can be expressed as:

½CV²

A 10 µF capacitor charged to 20 V is disconnected and connected in parallel with an uncharged 10 µF capacitor. Final voltage is:

10 V

In a charging RC circuit, at time constant τ, the capacitor voltage is approximately:

63% of supply voltage

In AC circuits, a capacitor behaves as:

A frequency-dependent resistor

Capacitive reactance decreases when:

Frequency increases

If two identical capacitors are connected in parallel, total capacitance is:

Twice the individual capacitance

Why does a capacitor initially behave like a short circuit in DC?

Voltage across it is initially zero

If frequency approaches infinity, capacitive reactance approaches:

Zero

Two capacitors store equal charge. Which has greater energy?

The one with higher voltage

In series capacitors, the smallest capacitor:

Has the highest voltage

A capacitor connected to AC will continuously:

Charge and discharge

The formula for the time constant in an RC circuit is:

τ = RC

The symbol used for the time constant is:

τ (tau)

After one time constant (1τ) during charging, the capacitor voltage reaches approximately:

63.2% of the final voltage

During discharging, the voltage after one time constant drops to about:

36.8% of the original voltage

The approximate time required for a capacitor to be almost fully charged or discharged is:

5 time constants

After two time constants during charging, the capacitor voltage reaches approximately:

86.5% of the final voltage

After three time constants during charging, the capacitor voltage reaches approximately:

95% of the final voltage

After four time constants during charging, the capacitor voltage reaches approximately:

98.2% of the final voltage

After five time constants during charging, the capacitor voltage reaches approximately:

99.3% of the final voltage

The RC time constant determines how quickly a capacitor charges and discharges:

Rate of charging and discharging of the capacitor

What is AC?

Changing direction current

Unit of frequency is:

Hertz

RMS value represents:

Average power equivalent

Inductance opposes:

Change in current

Unit of inductance:

Henry

In an inductive circuit, current:

Lags voltage

Formula for inductive reactance:

$$X_L = 2 ext{π}fL$$

Transformer works on:

Mutual induction

Step-up transformer:

Increases voltage

If secondary turns > primary turns:

Step-up

If frequency increases, inductive reactance:

Increases

If transformer secondary is shorted:

Primary current increases

Time constant of inductive circuit:

$$rac{L}{R}$$

Eddy currents cause:

Heat loss

Ideal transformer efficiency is:

100%