Past Paper questions Flashcards

1
Q

What is the significance of the RMS value of a voltage

A

The RMS voltage tells us the average power dissipated in a resistance

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2
Q

How many diodes are in a half wave rectifier circuit

A

1

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3
Q

How many diodes are in a full waves rectifier circuit

A

2

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4
Q

How many diodes are in an inverting rectifier circuit

A

4

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5
Q

For a sin wave what is the equation for Vr.m.s

A

Vpk/root2

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6
Q

What is the integral for the Vr.m.s

A

V^2r.m.s=1/T x integral ((v(t)^2)dt) between 0 and T/2

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7
Q

What is burst control of a load

A

In burst control the load is switched on for an integer number of whole cycles then switched of for an integer number of whole cycles. then repeats

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8
Q

Is burst and phase control of a load used for control of DC or AC loads

A

AC

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9
Q

What is phase control

A

The load is switched off part way through each half cycle

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10
Q

Are SCR’s used for AC or DC

A

AC

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11
Q

Why cant a SCR be used for an AC supply

A

Because SCR’s are switched off by reducing the voltage across it to 0V. This is not achievable for DC

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12
Q

What are some benefits if linear regulators compared to switch mode regulators

A

Electrically quiet, simple, cheap, do not require external components beyond smoothing capacitor

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13
Q

What are some disadvantages of linear regulators co9mpared to switch mode regulators

A

Vin must be greater than Vout for a linear regulator

Linear regulators are not very efficient, they have a large voltage drop (through resistor as heat)

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14
Q

what sort of conversion are buck, boost and buck-boost converters used for

A

DC-DC

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15
Q

In a Boost converter what is the Voltage in the inductor equal to

A

VL=Vin when charging

VL=Vin-Vout when discharging

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16
Q

For a boost converter what is the output voltage equal to

A

Vo=Vin/(1-D)

17
Q

For a boost converter what is the output current equal to

A

Io=(1-D) x Iin

18
Q

What is true for both Buck and boost converters

A

Pin=Pout

19
Q

For a buck converter What is the Vout equal to

A

Vout=DVin

20
Q

For a buck converter what is the Iout equal to

A

Iout= 1/D x Iin

21
Q

During charging of the inductor in a buck convertor what is the voltage across the inductor

A

VL=Vin-Vout

22
Q

During discharging of the inductor for a buck convertor what is the voltage across the inductor

A

VL= -Vout

23
Q

What is the conduction power loss for a MOSFET

A

Pcond=Rds,on x I^2r.m.s

24
Q

When charging how would you calculate the current for an inductor

A

iL = DT x di/dt

25
Q

When discharging how would you calculate the current for an inductor

A

iL= (1-D)T x di/dt

26
Q

What is the maximum and miniumum value for the current in a buck converter

A

Iave +- iL/2