Circuits

Question 1

What is the definition of the time constant for an RC circuit?

Answer 1

The time to increase the charge stored by 63% of the difference between initial charge and full charge, or the time taken to discharge the capacitor to 37% of initial charge.

Question 2

When can an uncharged capacitor be considered fully charged in an RC circuit?

Answer 2

After a time approximately equal to 5τ

Question 3

In an RC circuit when can an originally fully charged capacitor be considered fully discharged?

Answer 3

After a time approximately equal to 5τ

Question 4

What is capacitive reactance?

Answer 4

The opposition of a capacitor to the changing current

Question 5

State Lenz’s Law

Answer 5

The induced current is always in such a direction as to oppose the change that is causing it.

Question 6

What is the definition of inductance?

Answer 6

The inductance of an inductor is one Henry if an e.m.f. if one volt is induced when the current is changing at a rate of one ampere per second.

Question 7

Definition of back EMF

Answer 7

An e.m.f. that is induced in the coil because the current of the coil is changing and acts against the increase in current creating a time lag.

Question 8

What is stored in the magnetic field around a current-carrying inductor?

Answer 8

Energy

Question 9

What opposes an inductor when it’s changing current?

Answer 9

Inductive reactance

Question 10

Why would a diode be included in a circuit with an inductor?

Answer 10

To protect components from large back emf

Question 11

How does the use of a capacitor in a circuit allow high frequency signals to be picked up?

Answer 11

As capacitors have low reactance/impedance for high frequencies more current (and power) will be delivered to the components in the circuit at high frequencies.

Question 12

How does the use of an inductor allow low frequency signals to be picked up in a circuit?

Answer 12

Inductors have low reactance/immanence for low frequencies so more current (and power) will be delivered to the components in the circuit at low frequencies.

Question 13

Why is it more effective to use an inductor instead of an additional resistor to ensure maximum energy through the circuit?

Answer 13

A resistor would dissipate energy, whereas an inductor would store energy which could then be disbursed in the circuit.