Posterous theme by Cory Watilo

 

 

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>>

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Click here to download:
Q=It and V=EoverQ worksheet.doc (57 KB)
(download)

 

 

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"

 

 

2.16

24 November 2010

10:31

·         2.16 understand that current is the rate of flow of charge

Demo

·         Ball of aluminium foil swinging between two metal plates which are charged by Wimshurst generator

·        

 

 

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

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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

 

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