CP9a Electric circuits

CP9a - Electric circuits

Open Ended

Most wires are made of copper. Suggest reasons below for this.

How the structure of atoms in metals, make metals good conductors.

• Identify the parts of an atom and

• Describe the role of delocalised electrons

• Distinguish between electron flow and conventional current

Recap - the structure of the atom

• Atoms are largely empty space.

• A tiny dense nucleus contains positively charged protons and neutral neutrons of about the same mass of 1 atomic unit

• Negatively charged electrons with negligible mass surround the nucleus in cloud

• The overall charge is neutral

Multiple Choice

Most of the atom is filled with

• electrons
• empty space
• the nucleus
• protons

Multiple Choice

The positively charged particles of an atom are the ________.

• electrons
• protons
• neutrons
• protons & neutrons

Multiple Choice

In an atom, what is the number of electrons equal to?

• The number of protons.

• The number of neutrons.

• The number of molecules.

Multiple Choice

What number indicates the nucleus?

• 1
• 2
• 3
• 4

Multiple Choice

What number indicates an electron?

• 1
• 2
• 3
• 4

Multiple Choice

What number indicates a neutron?

• 1

• 2

• 3

• 4

Multiple Choice

Which particles make up the nucleus of an atom?

• protons and neutrons

• electrons and protons

• electrons, protons, and neutrons

Multiple Choice

An electron has a _____ charge.

• negative
• positive
• neutral

Multiple Choice

Complete the table for the first row:

• 1. = +1

  2. = 0

• 1. = 0

  2. = 1

• 1. = +1

  2. = 1

Multiple Choice

Complete the table for the second row:

• 3. = nucleus

  4. = 0

  5. = 1

• 3. = electron shells

  4. = 1

  5. = 1/1800 negligible

• 3. = electron shells

  4. = 0

  5. = 1

Multiple Choice

Complete the table for the third row:

• 6. nucleus

  7. 1

• 6. proton

  7. 1/1800 negligible

• 6. electron

  7. 1/1800 negligible

Electron shells

• Look at the diagram of a sodium atom. How many electrons and protons does it have?

• Notice that the electrons are arranged in orbits called shells.

• The inner shell can have up to 2 electrons in it and the next shells can have up to 8 electrons in them

• How many electrons does the sodium atom have in it's outer shell?

Delocalised electrons in metals

• Atoms in metals have very few (1 -3) electrons in the outer shell

• They are weakly attracted, so can move between the atoms

• They are called delocalised electrons

How are metals good conductors?

• When a voltage is put across a conductor, the electrons begin to drift in one direction.

• Current is now flowing in the circuit

• Notice that the electrons are being pushed away from the negative terminal and attracted towards the positive terminal

• This is called electron flow

Conventional current & current flow

• Diagrams and all electricity rules show the current going from the positive to the negative terminal (the direction the scientists assumed it to be)

• This is called 'conventional current'

Multiple Select

Which of the following are properties of a metal: (you should select more than one)

• Good conductor of heat and electricity

• Brittle (break easily)

• Malleable (able to bend without breaking)

• Luster (shiny)

• Dull

Multiple Choice

Silicon has an atomic number of 14. How many electrons does it have in it's outer shell?

• 1

• 2

• 3

• 4

Multiple Choice

Which electrons in a metal atom can form current?

• Just the electrons in the outer shell

• All the electrons in the atom

Multiple Choice

What do the arrows in the circuit represent?

• conventional current flow

• electron flow

Multiple Choice

By convention, current is defined as flowing from ______________ to ______________.

• positive, negative

• negative, positive

Open Ended

Challenge - Write a sentence to describe how electrons move in a circuit, when a potential difference is applied. Use as many keywords as you can, in as few as words as possible.

Open Ended

Give yourself a mark out of 5. How many of these points did you get: Weakly attracted outer electrons, are free to move. When a voltage is applied, they are repelled from the negative and attracted to the positive terminal

end of lesson 1

Drawing circuit diagrams

• To draw circuit diagrams we use standard components symbols that can be understand universally

• Use the next slides, to see how many components you can identify.

• Note cells convert chemical energy to electrical energy when connected to a circuit.

• Batteries are actually two or more cells working together.

Multiple Choice

This is the circuit symbol for ...

• an AC current source

• a battery

• a single cell

Multiple Choice

This is the symbol for a:

• Closed switch

• Push switch

• Trap door

Multiple Choice

This is the circuit symbol for ...

• a Van de graaff generator

• an ammeter

• a voltmeter

Multiple Choice

This is the circuit symbol for ...

• an AC current source

• a voltmeter

• an ammeter

Multiple Choice

This is the symbol for a ...

• Wire

• Battery

• Fuse

Multiple Choice

This is the symbol for a ...

• Bulb

• Battery

• Horn

Multiple Choice

what is this symbol for?

• light bulb

• cell

• battery

Multiple Choice

Which instrument is shown in the picture?

• voltmeter

• ammeter

• multimeter

• thermometer

Multiple Choice

this is the symbol for a _____?

• switch

• light

• battery