Topic 1: DC Basics

Question 1

Charge

What is Charge measured in ?

Answer 1

Coulombs, Q or q

Question 2

Charge

Define Charge

Answer 2

Quantity of electricity. Charge is Conservative i.e. cannot be created or destroyed

Question 3

Charge

What is the electrical Charge of an Electron ?

Answer 3

The small and constant quantity of NEGATIVE electricity in an electron is 1.602x10(-19) Q

Question 4

Charge

What is a Charged Atom defined as.

Answer 4

An Ion

Question 5

Charge

Electron Accumulation means…

Answer 5

A negative charge of -q coulombs

Question 6

Charge

Electron Depletion means…

Answer 6

A positive charge of q coulombs

Question 7

Current

What is Current measured in?

Answer 7

Amperes, I or i

Question 8

Current

Define Current

Answer 8

The rate of movement of charge through a circuit

Question 9

Current

State the relationship between electrical current and time

Answer 9

Q = It ( 1 amp = 1 coulomb per sec)

Question 10

Charge

How many electrons does a coulomb possess

Answer 10

6.24x10(18) electrons

Question 11

Current

What is the Current of an Amp

Answer 11

6.24x10(18) electrons/sec

Question 12

Voltage

What is voltage measured in?

Answer 12

Volts, V or v

Question 13

Voltage

Define Voltage

Answer 13

Voltage or potential difference may be defined as the energy required to move a unit of charge from one point to another

shown as; V = dw/dq
where w is energy

Question 14

Voltage

What is 1 volt equivalent to?

Answer 14

1 volt = 1 Joule/coulomb

Question 15

Voltage

Describe the Current and Voltage relationship

Answer 15

I = Q/t therefore;

W = VQ = VI x t

Question 16

Ohm’s Law

State the Equation for ohm’s law

Answer 16

V = IR

Question 17

Electrical Energy

What happens when current flows in a resistant circuit ? Provide the equation that represents this.

Answer 17

Energy is Consumed

W = I^2xRxt ( Joules )
Joules = Watts/second

Question 18

Electrical Energy

kWh is used commercially, what is 1 kWh in Joules?

Answer 18

1kWh = 1kW x h = 1000W x (60 x 60 )s = 3600000J = 3.6 MJ

Question 19

Electrical Power

What is Power measured in?

Answer 19

Watts, P

Question 20

Electrical Power

Define Electrical Power then describe the relationship between Power Energy and Time displaying the relevant equation(s).

Answer 20

Rate of Work Done

P = energy/time = ( I^2 x R x t)/t = I^2 x R

rearranging gives; P = VI

Question 21

Kirchoff’s Current Law

State one rule of Kirchoff’s Law

Answer 21

the sum of currents entering a point/junction is zero

entering a point - positive
leaving a point - negative