Electricity Merit Vol 2

Open vs Close Switch. Why are Voltmeter readings different? ONE(B) 2024

Open: voltmeter would read 12V.

Closed: voltmeter would read less than 12V.

Reason Closed: Current flows through circuit. Reading less than 12V. Due to potential drop across internal resistance

We have Area, Flux Density, Turns, and Change in time. How can we calculate EMF? TWO(B) 2024

Magnetic Flux = Flux Density * Area

Voltage = N * Magnetic Flux / t

With inductance and Resistance. How can we calculate the phase difference between supply voltage and circuit current, and choose the one that leads? THREE(B) 2024

1. Phase difference = tan-1(Xl -Xc/R)

2. If Phase difference +, Voltage leads, if -, then Current leads.

A inductor is brought into a circuit. Explain why headlamp bulb only comes after slight delay. TWO(c) 2023

1. Change in current produces Back EMF

2. Limits the rate of increase in current

3. Emf cannot be bigger than forwards voltage

4. The current builds up overtime

How do you calculate circuit current with capacitance, resistance, Vrms, frequency? 2022 One(B)

1. Find Xc = 1/Cw

2. Find Z = sqrt(Xc^2 + R^2)

3. Find I = Vrms/Z

Phasor Diagram ONE(C) 2022

1. VR is horizontal

2. VC is downward or if VL goes upwards

3. VS is 45degree

4. Angle between VS and VR is phase difference

How do you find current after a time constant. TWO(A) 2022

I = Imax(1 - e^-t/T)

How do you find avg induced voltage and state the direction across the inductor? TWO (c) 2022

1. V = L(I/t)

2. The induced voltage acts in the same direction as the source voltage (trying to maintain the current).

How do you find energy is capacitor? Describe the effect on energy after adding a dielectric between capacitor plates which is 7x the original one.

1. E = 1/2QV

2. E = 1/2CV^2

3. Introducing a dielectric increases the capacitance 7 times so energy stored increases 7 times.