I shall attempt to try to write some common misconceptions or
questions in physics that most students are usually wrong... Shall
build on as I teach along...
This applies to both Os and As levels
1) Potential difference and Electromotive force
Usually, papers ask you to explain or define (e.g. CGS 05 O
levels prelim physics paper 2, AJC H2 Physics 2009 Common Test
question)
For a start, both are measured in volts. Both are also defined
as the work done in bringing a unit charge somewhere.
Difference?
Potential difference between 2 points is defined as the work
done in bringing a unit charge across 2 points
Electromotive force is defined as the work done in bringing a
unit charge around a complete circuit
2) Centre of gravity and centre of mass (2nd one is for
interest)
C.G. is the point where WEIGHT of object SEEMS to act on (not
Mass)
C.M. is the point where WEIGHT of object SEEMS to act on (not
Mass) in a uniform
gravitational field.