2008 - JAMB Physics Past Questions and Answers - page 4

To correct and A.C generator with a D.C generator the slip ring is replaced with split-ring communicator

Efficiency = (power output)/power input x 100%

= 1_s V_S x 100% 1_p

V_p

∴ (80)/100 = (50)/I_P x 200

I P = (50 x 100)/80 x 200 = 3.125 A

Max kinetic energy = Energy of incident electron - work function. EK = hf - w

= 6.6 x 10^-34 x 6.7 x 10¹⁴ - 3 x 10^-19

= 4.422 x 10^-19 - 3 x 10^-19

= 1.422 x 10^-19J

Zener diode is useful in stabilized power supply i.e to keep steady the voltage of a power supply.

Heating a pure semiconductor increases the mobility of electrons and holes and hence the conductivity. thus, the resistance decreases on heating

Transistor is used for amplification of current, power and as a switch in logic gates.

Electrical work W = QE,

Where Q is the quantity of change and E is the electromotive force.

∴ E = W = FxDQ_It

Where D is the displacement,I = current and t = time

But dimension of force,

= unit of mass x unit of Acceleration

= unit of mass xunit of velocityunit of time

= unit of mass x unit of displacement__unit of time x unit of time

ML/T² = MLT^-2

∴ Dimension of emf E

= MLT^-2L = ML²T^-3I^-1__IT

R² - P² + Q² = 12² + 5²

= 144 + 25 = 169

∴R = √169 = 13N

∴ angle between the forces is 90^o

The force which is centripetal

F = MV²_R

=5 x 7²3.5

= 70

V = √(Fr) and if F is tripped, then

V = √(3Fr)/m

= √(3x70x3.5)/5

= 12.1ms^-1

Smooth plane has negligible friction

∴ only the resultant of the perpendicular forces is acting on the body, which is given as

F =

√ 8² + 6² 

=

√ 64 + 36 

=

√ 100 

= 10N

But F = Ma

∴ a = ^F/_M = ¹⁰/₄ = 2.5 ms^-1