Chapter 1- Voltage, Current and Resistance

Question 1

What is an atom

Answer 1

• Smallest particle of an element that retains its characteristics (Examples : Hydrogen, Oxygen, Carbon),and is characterized by a sharing of the chemical properties of the element and a nucleus with neutrons, protons and electrons.

Question 2

What gives the atomic number of an element

Answer 2

• The number of protons gives the atomic number of an element.

Question 3

View the periodic table here

Answer 3

Question 4

Give the charge for the protons, neutrons and electrons of an atom

Answer 4

• Protons are positively charged particles
• Neutrons are uncharged particles
• Electrons are negatively charged particles

Question 5

In its normal/neutral state, what does an atom have?

Answer 5

In its normal or neutral state, an atom has an equal number of protons and electrons.

Question 6

What does each of the known elements have

Answer 6

• Each of the known elements has a unique atom structure and a unique atomic number

Question 7

In the periodic table, atoms are arranged according to what?

Answer 7

In the periodic table, atoms are arranged according to their atomic number

Question 8

The positive charge of a proton is equal to what? Why?

Answer 8

• The positive charge of a proton is equal and opposite to the one of an electron, because positive charge cancels the negative charge, therefore, the atom has a net charge of zero

Question 9

What is electrical charge symbolised by? Why?

Answer 9

• Electrical charge is symbolised by Q, because:

Q is charge in coulombs (C)

Question 10

What is static electricity

Answer 10

Static electricity is the presence of a net positive or negative charge in a material

Question 11

What number determines the characteristics of the element?

Answer 11

The atomic number determines the characteristics of the element

Question 12

What are the same in all elements, but their numbers differ?

Answer 12

Smaller particles like electrons or protons

Question 13

Each atom of the known 109 elements have a unique number of what?

Answer 13

Each atom of the known 109 elements has a unique number of protons

Question 14

What is referred to as ‘‘atomic number’’, that all 109 elements have a unique number of?

Answer 14

Protons

Question 15

Elements in the periodic table are arranged according to what?

Answer 15

their atomic number

Question 16

What number determines the characteristics of an element?

Answer 16

The atomic number

Question 17

In an atom, what forms the nucleus?

Answer 17

Neutrons and Protons

Question 18

What orbits the nucleus in an atom?

Answer 18

Electrons orbit the nucleus in an atom.

Question 19

What is the charge of one electron ( or one proton ) in an atom?

Answer 19

1.6x10-19 C (C stands for Coulomb)

Question 20

What does C stand for?

Answer 20

C stands for Coulomb

Question 21

In its neutral state (without external forces applied), the atom has the same amount of what?

Answer 21

positive and negative charges (i.e the same number of protons and electrons).

Question 22

What makes the atom neutral

Answer 22

Positive and negative charges cancel each other making the atom neutral.

Question 23

Electrons orbit the nucleus at what distance from the centre

Answer 23

a discrete ( synonym - distinct ) distance

Question 24

In the case of electrons, the closer from the nucleus the more what?

Answer 24

The closer from the nucleus the more tightly bound to it and the less amount of spare energy.

Question 25

Electrons orbiting at the same distance from the nucleus have the same what?

Answer 25

Electrons orbiting at the same distance from the nucleus have the same energy level.

Question 26

Electrons are grouped in energy bands known as \_\_\_\_\_\_. Why?

Answer 26

Electrons are grouped in energy bands known as shells, because electrons orbiting at the same distance from the nucleus have the same energy level

Question 27

Regarding Electrons, each shell has a what?

Answer 27

Each shell has a fixed number of electrons given by 2N^2 (N being the shell number, starting at 1 for the closest shell to the nucleus).

Question 28

Depending on \_\_\_\_\_\_, atoms will have a certain amount of shells.

Answer 28

Depending on their atomic number (number of protons)

Question 29

For each element, the shell further from the nucleus is called the \_\_\_\_\_\_\_

Answer 29

the valence shell. This shell and its composition will determine most of the element properties.

Question 30

What will the valence shell determine?

Answer 30

This shell and its composition will determine most of the element properties.

Question 31

Electrons on the valence shell are known as what?

Answer 31

Electrons on the valence shell are valence electrons.

Question 32

What can valence electrons do with a sufficient amount of energy?

Answer 32

These electrons, with a sufficient amount of energy, can free themselves from the bond to the nucleus and become free electrons.

Question 33

What will be the source of the electrical current

Answer 33

The movement of valence electrons freeing themselves from the bond to the nucleus will be the source of electrical current.

Question 34

Some elements like metals have free what?

Answer 34

free electrons without the need of an external source of energy.

Question 35

Why are metals good conductors?

Answer 35

some metals have free electrons without the need of an external source of energy

Question 36

What is the best conductor

Answer 36

The best conductor is silver.

Question 37

Why is copper the most widely used conductor

Answer 37

Due to the cost of silver, copper is the most widely used.

Question 38

What other element is a good conductor, apart from metals and silver

Answer 38

Gold is also a good conductor and is used when resistance to corrosion is required.

Question 39

When is gold used as a conductor

Answer 39

when resistance to corrosion is required.

Question 40

Semi-conductors have ____ electrons on their valence shell

Answer 40

Semi-conductors have four electrons on their valence shell.

Question 41

What do semi-conductors require

Answer 41

They require some external source of energy to free electrons.

Question 42

Why do semi-conductors have 4 electrons on their valence shell

Answer 42

They require some external source of energy to free electrons.

Question 43

Why can't insulators carry electrical current

Answer 43

Insulators cannot free electrons and therefore cannot carry electrical current

Question 44

If an atom loses electrons or gains protons, what happens?

Answer 44

it will have a net positive charge and is called a cation.

Question 45

If an atom gains electrons or loses protons, what happens?

Answer 45

it will have a net negative charge and is called an anion.

Question 46

What are isotopes

Answer 46

Atoms of the same element that differ in their numbers of neutrons are called isotopes