Resistive, Capacitive, EM devices and Circuits

Question 1

Meaning of the 4 bands on a resistor

Answer 1

The First digit, Second digit, Decimal multiplier, and tolerance.

Question 2

Open Circuit

Answer 2

An open circuit prevents current.

Question 3

Short circuit

Answer 3

A short circuit causes more current than usual.

Question 4

Rheostat vs Potentiometer

Answer 4

A Rheostat controls the current in a circuit while a potentiometer is used to divide the voltage.

Question 5

Wheatstone Bridge

Answer 5

Used to measure an unknown resistance. The standard resistor is adjusted so the ammeter is 0 to balance the bridge.

Question 6

Bleeder current

Answer 6

The current left after the total load current is subtracted from the total current.

Question 7

Root Mean Squared (RMS) or Effective Value

Answer 7

Relates the amount of a sine wave of voltage or current of AC to the DC value that will produce the same heating effect.

Question 8

Oscilloscope

Answer 8

An AC voltmeter with graphical voltage against time displays.

Question 9

Method of Branch Currents

Answer 9

1- Assume and indicate current directions at all branch points.
2- Mark voltage polarity consistent with all current directions for resistors.
3- Identify loops and write loop equations for voltage drops using KVL.
4- Solve simultaneous equations to get branch currents.
5- Use Ohm’s law to calculate voltage drops across individual resistors.

Question 10

Node-Voltage Analysis

Answer 10

1- Assume and indicate current directions at all branch points.
2- Mark voltage polarity consistent with all current directions for resistors.
3- Identify principle nodes and write equations for the currents in and out of the nodes using KCL.
4- Solve simultaneous equations to find node voltages.
5- Use Ohm’s law to calculate current across individual resistors.

Question 11

Capacitor

Answer 11

A capacitor consists of two conductors separated by a dielectric to store electric charge as well as energy in the electric field.
Capacitors block steady DC signals but pass AC signals.

Question 12

How to increase the capacitance

Answer 12

A larger plate area increases the capacitance.

A thinner dielectric increases the capacitance.

Question 13

Capacitive current

Answer 13

The current that flows when AC voltage is applied to a capacitor.

Question 14

Capacitive reactance

Answer 14

The opposition a capacitor offers to the flow of sinusoidal wave alternating current.

Question 15

Lenz’s law

Answer 15

The direction of induced current must be such that it opposes the action that caused it.

Question 16

Self Inductance

Answer 16

The inductance caused by an alternating current.

Question 17

Mutual Inductance (Lm)

Answer 17

Occurs when the alternating current flowing through one conductor creates a changing magnetic field which induces a voltage in a nearby conductor apart from inducing voltage in the original current carrying inductor.

Question 18

Transformers

Answer 18

Has two or more windings with mutual inductance.
The primary winding is connected to an AC power source.
The secondary winding is connected to the load.

Question 19

Inductive reactance

Answer 19

The additional opposition of an inductor to sine wave alternating current.