Electronics

Question 1

Name the SI units

Answer 1

Meters

Kilograms

Seconds

___________________

Volt: voltage

Ampere: current

Ohm (Ω): resistance

Watt: power

Joule: energy

Coulomb: charge

Hertz: frequency

Farad: capacitance

Henry: inductance

Siemen: conductance

Weber: magnetic flux

Tesla: magnetic field strength

Kelvin - temperature

Candela - luminous intensity

Mole (mol): A quantity of something where the numer of units is equal to Avogadro number, 6.02214076 × 10²³.

Question 2

What are the numerical prefixes commonly used in engineering?

Answer 2

10⁺¹² - tera - T

10⁺⁹ - giga - G

10⁺⁶ - mega - M

10⁺³ - kilo - k

10⁰

10^-3 - milli - m

10^-6 - micro - µ

10^-9 - nano - n

10^-12 - pico - p

Question 3

Convert 300K to °C

Answer 3

300K = 26.85 ºC

300 - 273.15 = 26.85

Question 4

Convert 50 °F to °C

Answer 4

50 °F = 10 °C

(50 - 32) x 5/9 = 10

Question 5

What is charge?

Answer 5

Electric charge is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charge: positive and negative. Like charges repel each other and unlike charges attract each other. This is electrostatic attraction or repulsion.

The unit of charge is the coulomb.

The charge of an electron is:

e = -1.602176565 x 10^-19 coulomb

or

1 coulomb = 6.241509343 x 10¹⁸ electrons

Question 6

What is the definition of an electric current?

Answer 6

An electric current is the rate of flow of electric charge (q) past a point or region.

The positive direction is the direction that the positive charge is moving in. However, electrons are negatively charged and so flow towards the positive terminal of a battey.

1 ampere is equal to 1 coulomb per second which is 6.241509343 x 10¹⁸ electrons.

Question 7

What is voltage?

Answer 7

Voltage is an electrical potential difference that provides the force to push charge. It is sometimes called electromotive force. In the gravity analogy it is the force taking the rocks to the top of the mountain.

The voltage between two points can be defined mathematically as the change of energy experienced by a charge.

Question 8

That is Faraday’s constant?

Answer 8

The Faraday constant, denoted by the symbol F and sometimes stylized as ℱ. The number represents the magnitude of electric charge per mole of electrons.

Question 9

What is electrical power?

Answer 9

Power is defined as the rate energy (U) is transformed or transferred over time.

The unit of power is the watt (W).

It can also be measured in joules/second.

1 watt = 1 joule/second

P(Watts) = I(Ampere) x V(Volts)

Question 10

What is energy?

Answer 10

In physics, energy is the quantitative property that must be transferred to an object in order to perform work on, or to heat, the object.

The unit of energy is the joule (J).

1 joule is equal to the work done by a force of one newton when its point of application moves one metre in the direction of action of the force.

Question 11

What is the difference between Power and Energy?

Answer 11

Energy = Power x Time

Power is a staic measure of what could be done, energy is the the a measure of the electricity used over time.

In SI units we can say:

1 joule of energy = 1 watt second

Question 12

How you you treat resistors in series?

Answer 12

• Resistors in series sum together
• They share the same current
• voltage distributes amounst series resistors, with the largest voltage across the largest resistor.

Question 13

How do you treat resistors in parallel?

Answer 13

In parallel you can use (1), the sum of 1/R. However, the resistance is the reciprocol term of the conductance. Using the conductance its a simple sum of, much like resistors in series.

Question 14

What are the 3 power equations?

Answer 14

Question 15

What is Kirchhoff’s Current Law?

Answer 15

A node does no accumulate current, thus the net current must be zero. Or, the sum of the currents going in is equal to the sum of the current going out of the node.

Question 16

Name 4 circuit analysis methods

Answer 16

1. Application of fundamental laws
2. Node voltage method
3. Mesh current method
4. Loop current method

Question 17

What is Kirchhoff’s Voltage Law?

Answer 17

The sum of voltage rises in the circuit, minus the sum of the voltage falls, is equal to zero.

Question 18

Multiplying signs

Answer 18

Same sign is positive, opposite signs give a negative.

+ X + = +

• X - = +

+ X - = -

• X + = -

Question 19

Dividing signs

Answer 19

Matching signs are positive and mixed signs are negative

+ / + = +

• / - = +

+ / - = -

• / + = -