Resistance ISA

Here’s the plan:

• • • • • • • • •

Thurs 20 th

– Graph of current against resistance. Theory of heat/resistance.

Friday 21st

– Background, context, research, CRN.

Mon 24 th

– CRN (continued) Table and Paper 1 Prep

Tues 25 th

– Paper 1

Wed 26 th

– Practical (am), Graph (pm)

Fri 28 th

– Paper 2 Prep

Mon 1 st

– Paper 2 Prep (again!)

Tues 2 nd

– Paper 2? (it’s a pm lesson)

Wed 3 rd

– Paper 2?

The Background

Filament lamp symbol The filament lamp is a common type of light bulb. It contains a thin coil of wire called the

filament

. This heats up when an electric current passes through it and produces

light

as a result.

Higher tier only

An electric

current

flows when

electrons

move through a

conductor

, such as a metal wire. The moving electrons can

collide ions

with the in the metal. This makes it more difficult for the current to flow, and causes

resistance.

As the temperature increases, the metal ions

vibrate

more. There are more

collisions

with the electrons and so the

resistance increases

.

Electricity in wires is a flow of electrons along the wire. As the

electrons

move along the wire they

collide

collision make the atoms

vibrate

with the copper atoms (ions). These more…which makes the metal

hotter.

This in turn, leads to

more collisions

, and therefore

more resistance.

Resistance

is a measure of how much a material ‘tries’ to stop electricity passing through it.

The Context Part 1

: When you first switch on a filament bulb:

1. The filament wire is cool.

2. The resistance is low, so this causes a high current to flow.

3. The high current leads to a ‘surge’, which in turn causes resistance to increase.

4. The surge only lasts 0.1 s, but causes the filament wire to heat up suddenly, called ‘thermal shock’.

5. This may cause the wire to melt and break at a weak point.

The Context Part 2

• • •

Consumers

(that means ordinary people) want light bulbs that can be

switched on and off

thousands of times without the bulb blowing.

Light bulb manufacturers

need to know how the

resistance

changes.

in a bulb changes as the

current

HT: This will help them design bulbs that can

withstand the high resistance

avoid them blowing.

that occurs when bulbs suddenly heat up when first switched on, to

Your hypothesis…

• • You need to come up with this on your own.

Basic format: ‘I think that if I change ‘x’ then ‘y’ will ………..’ •

Hint:

Mention current and resistance, increase and/or decrease.

Research

• • Use the 4 resources provided to get further information and give you ideas on how to test your hypothesis.

You may also want to look back at the practical we did last week.

• • • • • • •

Candidate Research Notes

Hypothesis: ‘I think that if I change ‘x’ then ‘y’ will ………..’ Sources: Where did you find your information. You must be

specific – the full website address / title and author of the textbook to get 3 marks you need to be able to explain why you chose one source, what was better about it, why you rejected the other one and what was less good about it.

Method: Write up neatly as a list of notes to remind you in the exam Equipment: A list of what you’ll need Risk Assessment: any possible hazards / risks /controls -

table

Context: Light Bulb Manufacturers. Light bulbs need to able to withstand being switched on and off hundreds of times without the bulb blowing.

Planning your method….



Method

A short list of instructions in note form in order, not written in sentences spellings must be perfectly correct!!!

The equipment that is needed for the experiment - a list spellings again!

What are your independent, dependent and

variables

?

control Risk Assessment What are the potential Hazards, Risks and Control Measures involved in the experiment – put it in a table!