2.1 Conduction of electricity

Question 1

What is the law of conservation of charge?

Answer 1

The net charge in a system remains constant (provided charges cannot enter or leave).

Question 2

What is an electrical conductor?

Answer 2

A material, or piece of material, through which a charge can flow.

Question 3

Which particles have a positive charge?

Answer 3

Protons

Question 4

Which particles have a negative charge?

Answer 4

Electrons

Question 5

Which symbol is used to denote charge?

Answer 5

Q or q

Question 6

What is the SI unit of charge?

Answer 6

coulomb (C)

Question 7

What is the notation for an electron’s charge?

Answer 7

-e

Question 8

What is the notation for an proton’s charge?

Answer 8

e

Question 9

What does e= (when referring to the charge of a proton)?

Answer 9

e=1.602 * 10^-19 C

Question 10

Define electric current

Answer 10

The electric current through a conductor is the rate of flow of charge: the charge passing per unit time through a cross section of the conductor

Question 11

Equation for electric current

Answer 11

I = ΔQ/Δt

Question 12

Symbol for Electrical current

Answer 12

I

Question 13

Unit for electrical current

Answer 13

ampere (A) or C s^-1

Question 14

What is drift velocity?

Answer 14

The drift velocity is the flow velocity that a particle, such as an electron, attains due to an electric field.

Question 15

What is the typical thermal speed for an electron at room temperature?

Answer 15

10^5 m s^-1

Question 16

What is the symbol for drift velocity?

Answer 16

v

Question 17

Derive I=nAve

Answer 17

Over 1 second, electrons with drift velocity V travel through a wire of cross sectional area A. Distance Vt (t = 1) multiplied by area A gives a volume AV. This volume multiplied by the electron density of the material n, gives the number of electrons in volume V, nAV. The charge in the volume of material is found by multiplying the number of electrons by the elementary charge e, nAVe. This is the amount of charge passing through the wire every second, or current I. Therefore, I = nAVe

Question 18

What instrument is used to measure current?

Answer 18

Ammeter

Question 19

How does current change around a series circuit?

Answer 19

It doesn’t - it is the same all around.