Module 4 - Charge and current (Charge)

Question 1

What is electrical current

Answer 1

The rate of flow of charge.

Question 2

What is the base equation for current

Answer 2

I = Q/t

Question 3

What is the unit for current

Answer 3

Amps (A)

Question 4

True of False - Amperes is one of the S.I. Base units

Answer 4

True

Question 5

What is 1 amp equivalent to

Answer 5

1 amp = 1 Coulomb of charge passing a point in 1 second

Question 6

What is electrical charge

Answer 6

A physical property that measures how “charged” a particle or object is

Question 7

What is a charge carrier

Answer 7

Any body that carries an overall charge.

Question 8

What are the 2 base charges

Answer 8

Protons - positive
Electrons - negative

Question 9

What is meant by a neutral object

Answer 9

An object that has no overall charge

Question 10

What is the unit for charge

Answer 10

Coulomb (C)

Question 11

What is the smallest measurable charge

Answer 11

e: 1.60 x 10^-19 C

Question 12

What does it mean for other charges to be quantised by e

Answer 12

All (overall) charges on particles and objects are an integer multiple of e and can never be a non-integer

Question 13

What is the equation for charge with respects to e

Answer 13

Q= +- ne

Question 14

What is the charge of a proton

Answer 14

e: 1.60 x 10^-19 C

Question 15

What is the charge of an electron

Answer 15

-e: -1.60 x 10^-19 C

Question 16

Describe Milikans oil drop experiment setup

Answer 16

• Chamber with two horizontal metal plates Top plate - positive. Bottom plate -negative.
• Atomiser used to spray tiny droplets of oil into the area between the plates.
  -Microscope was set up to make it possible to see the tiny oil droplets as they floated in the air.

Question 17

Describe the Milikans oil drop experiment observation

Answer 17

• Initially, the oil droplets fell due to gravity
• Millikan then used x-rays to give the oil droplets a small, static electric charge by firing electrons onto them.
• Each droplet would pick up a different number of electrons and, therefore, a different amount of charge.
• Millikan applied an electric field which exerted an upward force on the negatively charged oil droplets.
• By carefully adjusting the electric field’s strength, he could balance the electric force with gravity, making some droplets “hover” in place.
• When a droplet was stationary, the force from the electric field exactly balanced the gravitational force on the droplet.

Question 18

Describe What the observation of the Milikans oil drop experiment showed

Answer 18

• By measuring the forces and calculating the charge on each droplet, Millikan discovered that the charges were always multiples of a smallest, fixed amount of charge. This smallest unit was e, which provided strong evidence that electric charge is quantized, meaning it only exists in whole-number multiples of.

Question 19

What is the current in metals

Answer 19

The movement of electrons

Question 20

What is the current in electrolytes

Answer 20

The movement of ions

Question 21

In what system is the movement of ions a current

Answer 21

In electrolytes

Question 22

In what system is the movement of electrons a current

Answer 22

In metals

Question 23

What is the conventional current

Answer 23

The idea that current was positive and so flowed from the positive terminal to the negative terminal

Question 24

What is the electron flow in metals

Answer 24

The flow of electrons from the negative terminal to the positive terminal because it attracts the + ive and repels the - ive

Question 25

Which terminal has a higher electrical potential energy

Answer 25

The positive terminal

Question 26

What is Kirchoff’s first Law and what physical property is being conserved

Answer 26

At any given point in a circuit the sum of the current entering the junction is equal to the sum of the current leaving the junction. The property being conserved is Charge