elecs midterms 2nd sem

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

If the plate area is tripled and plate distance is halved, the new capacitance becomes:

Six times the original

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

Magnetic field lines:

Never intersect

If a magnet is cut in half:

Each half becomes a smaller magnet

The unit of magnetic flux is:

Weber

Increasing the number of turns in a coil:

Increases magnetic field strength

Soft iron is used in electromagnets because:

It magnetizes and demagnetizes easily

Electromagnetic induction requires:

Relative motion between conductor and magnetic field

If magnetic flux through a coil is constant, the induced EMF is:

Zero

The direction of induced EMF in a conductor can be determined using:

Left-hand rule for generators

Doubling both the current and number of turns in an electromagnet increases its strength by:

Four times

The unit ampere-turn represents:

Magnetomotive force

A solenoid differs from a relay because a solenoid has:

Movable core

In generator action, reversing the direction of motion will:

Reverse induced voltage polarity

The magnetic field around a straight conductor carrying electron flow toward you is:

Counterclockwise

The force exerted by an electromagnet on a magnetic material is inversely proportional to:

Square of distance

Transformer action differs from generator action because:

No mechanical motion is required

According to Faraday’s Law, induced EMF is proportional to:

Rate of change of magnetic flux

Lenz’s Law states that induced current:

Opposes the change causing it

If a conductor moves parallel to magnetic field lines, induced EMF is:

Zero

The unit of inductance is:

Henry

Self-inductance opposes:

Change in current

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