Current & Voltage Relationship

In this section 2.2:
U must be able to analyse the relation between current & Potential difference or sometimes known as voltage. By understanding the concept, we then can deduce a law called Ohm's law. The experiment that derives ohm's law is so important..please study& understand it properly..it quite famous in exam.,.

Here i give u list of important things that might be asked in exam

1. Define potential difference??
refer to your text/ reference book..then try to watch this

So basically,voltage is a work done per unit charge.

2.U must also be able to Plan & conduct an experiment to find the relationship between current & potential difference(voltage).

From this experiment u shud be getting a straight line graph of Voltage(V) vs Current (I). This experiment can come out in paper3 or paper2.
I want to remind u again, please make sure you know how to design this experiment.

3.Next, u must know
What is the relationship between current & potential diffrence (voltage)??
Voltage(V) is directly proportional with current (I). So if current(I) increases, voltage(V) also increases.

V α I

4. Then.. a must for u to know how to...
..State OHm's Law:
Current flowing through a conductor is directly proportional to potential diffrence at constant temperature.

Ohmic conductor obeys ohms law, i.e the graph of V vs I will be a staight line.
Non ohmic conductor wont give a straight line graph.

5. After that..u must be able to define RESISTANCE.
Resistance = ratio of voltage over current
i.e by formula R= V/I. the unit is ohm or Ω.

Watch this video to get a clear picture about all the relationship between V,I & R ...

Ohms Law

SPM 2009 : Welcome to Electricity

Dear all..now I’ll be discussing the next chapter Eleccity. B4 I go further, please bear in mind, in form 5, 3 out of the 5 topics comes from a word ElecTRO (electricity,electromagnet, electronics)

Electricity is the fundamentals..u really need to understand tis chapter coz its basic shall be applied in next 2 chapters..lets go deeper

2.1 Analysing Electric fields & Charge flow..

In this subtopic u must be able to:

1. Relate between electron (charge) flow & current:

How??? The flow of electrical charges produces electric current

So what does it mean by electrical charges?

In electrical current, the electrical charges are flowing electrons (-ve charged).

Thus the relationship is ..:If electrons are flowing, current will be flowing as well!

(Note:Check your reference book..refer details on Van Der Graff)

2. The next outcome..u must know how to define Current.
What is current?
Current is the rate of flow of charge
By formula: I = Q/t

I = current , unit is ampere(A)
Q =charge, unit is coulomb (C )
t = time taken (s)

3. Describe an electric field??

• an electric field is a region in which an electric charge experiences a force.
• lines of electric field moves away from + ve charge
• lines of electric field points towards - ve charge.

4. U must also know how to sketch the electric lines with correct direction:

5. U also need to describe the effect of electric field :
Watch these video..then refer yr reference book..or text book(pg46)

effect on pingpong ball

effect on candle flame

SPM2008 Physics Paper 3

SPM 2008 Physics K3