Don't get number..

[Jimmy G]

9. A resistor R is connected across the terminals of a cell of e.m.f. 12 V and internal resistance 1 Ohm. A voltmeter connected across the cell reads 10.5 V.

(a) Calculate the current from the cell, I.
(b) What is the resistance of R?

As well as all of 11, you'll need to show me that in class as it involves completing a graph.

And 12...

You need to go over the past paper style one too, it's confusing

[Admin]

James,
Q9. a. E = V + Ir, E = 12V, V = 10.5V, r = 1 ohm.
so 12 = 10.5 + I; I = 1.5 A
b. It is a series circuit so current is the same, V = IR, 10.5 = 1.5 R; R = 10.5 / 1.5 = 7 ohms.

With the graph questions remember that the gradient is -r, where it cuts the y-axis is your e.m.f. and your x axis itself is the current. If your line does not reach your y axis just add to the line yourself. Hope this helps.

[Jimmy G]

What do you mean "add to the line yourself"?
Continue it horizontally or continue the slope?

[Admin]

Continue the slope.

[S.McGrath]

in question 7

i keep getting R to be 4 ohms

but it says the answer is 12 ohms

[Admin]

The total resistance in the circuit is 4 ohms, V = IR ,where V = 12V and I = 3A. However the total resistance comes from three identical resistors in parallel.
Since 1/Rp = 1/R + 1/R + 1/R we get 3/R = 1/4, cross multipy and we get 12 = R. R = 12 ohms.

[S.McGrath]

i can only get the last multiple choice question

i dont think we have done the other 3 :O

[Admin]

Q10. A Only statement 1 is true,
the reading on the balance is weight - upthrust. The upthrust is due to the pressure change from the bottom of the cube being at a greater depth than the the top (unit 1 pressure at depth).
Q11. E
As a rule solid to liquid particles have a seperation of 1 to 10 and liquid to gas have a seperation of 1 to 10. Water and ice are the exceptions water is more dense than ice so the particles are close in water than ice. E can be the only answer (density, mass and volume unit 1).
Q12. B
W = QV and Ek = 1/2mv^2; conservation of emergy means W = Ek. from the information given Q = e, m = m and V = V.
eV = 1/2mv^2;
2eV/m = v^2
v = sqrt (2eV/m) (unit 2)
Sorry but we ahve covered them all.

[S.McGrath]

okay

[Jimmy G]

I dunno how to do question 7 onwards:S
It gives you R1, no supply voltage, it gives you I1 and a distance that makes the bridge balanced and they want you to find R2:S

[Admin]

James,
If they give you the distance in a piece of resistance wire and you know the lengths then the bridge is balanced when R1/R2 = I1/I2.

[Jimmy G]

Some questions I couldn't do but that's expected:)
Ty though:D

[S.McGrath]

i dont get Q24 in the homework :S

[Connor Einstein]

in question 22ci you are given 32 as horizontal component and 19.6 as vertical how do you work out initial speed and how do you work out theta

in 23b you are told a balloon is heated up to 33'C any change in pressure of the air inside the balloon is negligible but volume increases calculate the volume at 33'C

24 A,B&C

25 b sketch a graph of the PD across the capacitor against time for 10 seconds after switch is open numerical values are important you have a supply of 12v

25c sketch a graph of the Potential across the base of the transistor against time for 10 seconds after switch is open numerical values are important you have a supply of 12v

26 b ii the mean frequency of light emitted is 5.13 *10 ^ 14 calc wavelength of LED
iii determine light color emitted

[S.McGrath]

i dont get the whole of 26 (b)