Chapter #18 - Electrical Quantities

Question 1

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Current

Answer 1

The rate at whic electric charge passes a point in a circuit.

Question 2

What is needed for an electric current to flow?

Answer 2

1. A complete circuit
2. Something to ‘push’ the current around the circuit.
   - e.g. a battery

Question 3

Battery

Answer 3

2 or more cells connected end-to-end.

Question 4

Which way does current flow?

Answer 4

Current flows from the posotive terminal of the battery to the negative terminal.

Question 5

Direct current

Answer 5

An electric current which always flows in the same direction.

Question 6

How do most switches work?

Answer 6

By bringing 2 pieces of metal together to complete the circuit (though you cannot usually see this happening).

Question 7

Why are the wires in circuits made of metal?

Answer 7

Because metals are good conductors of electric current.

Question 8

Why are the metal wires coverd in plastic (in circuits)?

Answer 8

The metals are usually covered in plastic so that if the wires touch, the electric current cannot pass directly from one to another and cause a short circuit. Plastics arfe good insulators.

Question 9

What is the symbol and unit for current?

Answer 9

Symbol = I
Unit = Amps (A)

Question 10

What is actually travelling around the circuit?

Answer 10

Electric charge

Question 11

What does the power supply (the push) do to the charge in comparison to the current?

Answer 11

The power supply or batter proviedes the push needed to make the current flow. Thos push is the same force that causes electric charges to attract/repel eachother.

Question 12

Charge

Answer 12

Carried around a circuit by the current; negative charge is carried by electrons.

Question 13

Why are metals good electrical conductors?

Answer 13

Because they contain electrons that can mive about freely. While most electrons in a metal are tightly bound within their atoms, some are free to move about within the the material. These are called conduction electrons.

Question 14

How do we measure current?

Answer 14

Using an ammeter

Question 15

How must ammeters be connected to a circuit?

Answer 15

In a series

Question 16

In series circuits what is the current?

Answer 16

The current is the sam throughout the whole circuit.

Question 17

Why are polymers not good at conducting electricity?

Answer 17

Because all of the electrons in the material are tightly bound wu«ithin the atoms or molecules, so, theycannot move.

Question 18

What does a volatge do to a circuit. (turning in the powes supply)

Answer 18

A voltage (provided by battery or pwer supply) can start conduction electrons moving in one dirction throught the metal, and an electric current flows.

Question 19

What way do electrons travel in a circuit?

Answer 19

Since electrons have a negative electric charge, they are attracted to the posotive terminal of the battery.

Question 20

Which way does conventional electric current flow?

Answer 20

From positive to negative. But, in a metal it is the negativley charged electrons that move.

Question 21

What 2 things does an ammeter measure?

Answer 21

• The current in a circuit
• The rate at which electric charge flows past a point in a circuit.

Question 22

What is the equation for current?

Answer 22

Current = charge/time
I = Q/t

Question 23

What is the symbol and unit for charge?

Answer 23

Symbol = Q
Unit = Coulombs (C)