Substitute I1 = 1.0 A into (1), 3.0 = 1.0 + I2 I2 = 2.0A Substitute I1 = 1.0 A and I2 = 2.0A into I3 = I2 - I1 = 2.0 -1.0 I3 = 1.0A (b) Determine the potential difference VAB. [2 marks]
VAB = E2 - I2 R5 = 4.0 – (2.0)(4.0) = -4.0 V Section C 18
(a) (i) Faraday's law states that the induced electromotive force is directly proportional to the rate of change of magnetic flux. Lenz's law states that the direction of the induced current is such that it tends to oppose the change that produced it. OR
(2 M) (ii) – When an alternating potential difference is connected across a coil, a magnetic field is produced in the coil. // produce magnetic field -
-
The alternating current in the coil causes the magnetic field produced to be constantly changing. By Faraday’s law, this change of magnetic flux linkage experienced by the coil causes an induced e.m.f. in the coil. //produced induced emf By Lenz’s law, the direction of the induced e.m.f. (back e.m.f.) is such that it tends to oppose the change that caused its production (4 marks)
4
(b)
19
(a) Definition : The magnetic flux density or magnetic field strength of a magnetic field is 1 tesla (T) if a charge of 1 coulomb moving with a velocity of 1 m s-1 at right angles to the direction of the magnetic field experiences a force of 1 newton. (2 marks) (b)
The charged particle is stationary The charged particle is moving in a plane that is parallel to the magnetic field lines. (2 marks)
5
(c)
(i)
……………………(1)
F= 3
-19
7
= (8.4 x10 ) (1.6x 10 ) (3.4x10 ) = 4.6 x 10-14 N
……………………..(1)
(ii)
= 5.0 x 1016 m s-1
………………………………..(1)
(iii) (
r = 22.9 mm
)(
)
…………………….(1) ………………..(1)
(iv)
6
(d)
(i)
( ) (
)
(ii) If they are electrons, (
)(
)(
= 5.3 x 1011 m s-1
)
>speed of light
Therefore the charged particle causing the aurora cannot be electrons. (2 marks) 20
(a) (i)
Effective current for an AC current/ sinusoidal current, I = I0 sin ωt, which obtained by calculating time average of for the quantity I2 rms current is equivalent to DC value the measured value of AC current (1 m)
