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What is resonance frequency in LCR circuit.
If 660 joules of work was done by a battery in moving 110 coulombs of charge through a lamp, what was the voltage across the lamp?
3. a. Briefly explain Ohm’s Law (2 marks)
b. A 750 Watt electric convector heater is plugged into a 240 Volt power supply. A trolley
passing over the flex from the heater to the plug has caused the insulation to distort
and has reduced the resistance between the live and neutral wires to 60 Ohms.
(i) What is the rate of heat production (in Watts) at the point where the cable is
damaged? (Please show your calculations.) (1 mark)
(ii) The plug fitted to the heater flex carries a l3 amp fuse, is this the correct rating
for the appliance? (2 marks)
(iii) Would the correctly rated fuse have 'blown' as a result of the fault? (Please
show your calculations.) (1 mark)
b. Several years ago a change in the recognised colour conventions led to phase (live)
cables in industrial three phase power installations being changed from red, yellow
and blue to black, grey and brown. What are the implications for premises that have
not been rewired since that time? (4 marks)
c. Electric lighting is often overlooked as a potential source of ignition. List factors that
might lead to an electric light fitting becoming a source of ignition. (5 marks)
d. List the problems associated with the use of electric adaptors in the workplace and
why their use should be minimised. (5 marks
A single phase load draws 60 amps at a power factor of 0.9 lagging from a 230 v 50 hertz supply.
calculate
-apparent power
-true power
phase angle
the reactive power
Discharging RC circuit. • In the RC circuit shown, the battery has fully charged the capacitor, so Q0 = C E. Then at t = 0 the switch is thrown from position a to b. The battery emf is 20.0 V, and the capacitance C = 1.02 μF. The current I is observed to decrease to 0.50 of its initial value in 40 μs. (a) What is the value of Q, the charge on the capacitor, at t = 0? (b) What is the value of R? (c) What is Q at t = 60 μs?
A resistive position transducer with a resistance of 5000 and a shaft stroke of 5.0 in. is used in the arrangement of Fig. (4). Potentiometer R 3 R 4 is also 5000, and V T = 5.0 V. The initial position to be used as a reference point is such that R 1 =R 2 (i.e.. the shaft is at midstroke). At the start of the test, potentiometer R 3 R 4 is adjusted so that the bridge is balanced (V E =0). Assuming that the object being monitored will move a maximum distance of 0.5 in. toward A, what will the new value of V E be
)For a certain thermistor, its resistance at 32 o F is known to be 9 KΩ. And at 212 o F is 2KΩ. Find its resistance at 77 o F.
)An Iron-Constantan thermocouple (TC) is used to measure temperature between 0 o C and 300 oC at which it generates 5268 μV. If the thermal emf is 12500 μV relative to the reference junction at 20 o C. Estimate the measured junction temperature.
Three small positive electrical charges A, B and C are placed along a straight line. The distance between A and B is 12 cm. A and B have equal charges while C has twice the charge of each of A and B.
At what distance from B should C be placed in order for the resulting force on B to be zero?
Write ohm law
