2.19
24 November 2010
10:32
· 2.19 recall that:
· voltage is the energy transferred per unit charge passed
· the volt is a joule per coulomb.
V = E/Q or E = Q.V
V = Voltage (V)
E = Energy (J)
Q = Charge (C)
Therefore 1V = 1J/C
2.19 Top Tips for Calculations
24 November 2010
10:32
Top Tips for Calculations
(The bold writing is what you write down)
1. Write down what the question tells you. I = 4A, t = 20s
2. Write down what the question asks you for. Q = ?
3. Find an equation that links all these variable.
Formula → Q = I.t (1 mark)
4. Substitution → Q = 4 x 20 (1 mark)
5. Answer and Units → Q = 80C (1 mark)
2.17 and 2.19 Plenary worksheet
15 December 2011
09:30
<<Q=It and V=EoverQ worksheet.doc>>
2.17
24 November 2010
10:31
· 2.17 recall and use the relationship between charge, current and time:
charge = current × time
Q = I × t
Q = I.t
Q = Charge (C, Coulomb)
I = Current (A)
t = time (s)
How to remember this formula…
"If the exam is hard, don't ever Q(u)It"
2.18 answers
24 November 2010
10:32
· 2.18 recall that electric current in solid metallic conductors is a flow of negatively charged electrons
Conventional Current
· The flow of "imaginary" positive charges from + to -
· Why? Positive charges are repelled by the positive terminal of the battery and attracted to the negative terminal of the battery
· Symbol "I"
· Used in 90% of exam questions!
| |||||
| I | I | I |
Flow of Electrons
· The flow of real negatively charged electrons from - to +
· Why? Negative electrons are repelled by the negative terminal of the battery and attracted to the positive terminal of the battery

