Unit 2 Flashcards

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1
Q

What effect does a higher capacitance have on the rate of charge/discharge

A
  • increases time taken to charge

- longer for charge to build up on plates

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2
Q

Explain forward bias in terms of bands

A
  • voltage from supply lowers energy of conduction band
  • raises energy of valence band
  • less work is done
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3
Q

What is e.m.f

A

The work done in moving each coulomb of charge in the circuit

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4
Q

What is a.c

A

Alternating current

  • negative charges move back and forth
  • changes direction
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5
Q

What happens if the timebase is halved

A

There will be have as many waves as before on the screen

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6
Q

When is a Wheatstone bridge circuit balanced

A

When the voltmeter reads zero

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7
Q

When is a Wheatstone bridge circuit out-of-balance

A

When the voltmeter doesn’t read zero

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8
Q

What band is full in an insulator

A

Valance band (lower band)

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9
Q

How can a diode be reversed biased

A

N-type connected to positive terminals. No conduction occurs

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10
Q

How can a diode be forward biased

A

N-type connected to negative terminals. Conduction occurs

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11
Q

What is added to give a p-type

A

Indium

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12
Q

What is added to give a n-type

A

Arsenic

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13
Q

What is a semiconductor

A

Insulating material that has been doped with an impurity to increase its conductivity

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14
Q

What effect will heating a semiconductor have

A

Resistance will decrease

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15
Q

What effect does a higher resistance have on the rate of charge/discharge

A
  • increases time taken to charge
  • decreases current
  • decreases rate at which charges flow onto capacitor plates
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16
Q

Draw a graph of current against time for charging/discharging

A

(See notes for graph)

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17
Q

If resistance is increased across a resistor, what happens to the voltage and the current in the resistor

A
  • voltage increases

- current decreases

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18
Q

How would internal resistance and e.m.f be found from a voltage/current graph

A
Gradient = -r
Y-intercept = e.m.f
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19
Q

How would internal resistance and e.m.f be found from a resistance current graph

A
Gradient = e.m.f
Y-intercept = -r
20
Q

What is d.c

A

Direct current

  • flows in one direction
  • negative to positive
21
Q

When can e.m.f be measured

A

When there is no current flowing

22
Q

What is a capacitor

A

An electrical component that can store charge and therefore energy

23
Q

What is capacitance

A

The amount of charge stored per unit of potential difference

24
Q

What is internal resistance

A

The resistance of electrical source due to moving charges

25
Q

Explain reverse bias in terms of bands

A
  • voltage of supply will raise energy of conduction band
  • lower energy of valence band
  • more work is done
26
Q

How would the internal resistance of the cell be found

A

Voltmeter connected across the terminals of the cell

27
Q

What happens when a capacitor charges

A
  • voltage will increase until it equals supply voltage
  • current starts from maximum and decreases from zero
  • due to voltage increasing to supply
28
Q

Draw a graph of p.d against time for charging/discharging across resistors

A

(see notes for graph)

29
Q

Draw a graph of potential difference against time for charging/discharging a capacitor

A

(See notes for graph)

30
Q

How would you calculate Vreading on voltmeter on an out-of-balanced Wheatstone circuit

A
  • V1 = R1/R1+R2 x Vs
  • V3 = R3/R3+R4 x Vs
  • Vreading = V1 - V3
31
Q

What is lost volts

A

The potential difference used by the internal resistance

32
Q

What is current

A

The amount of charge flowing per second

33
Q

How is voltage found from a line on an oscilloscope

A

V = number of vertical divisions for amplitude x y-gain

34
Q

How is the period of a wave calculated from an oscilloscope reading

A

T = number of horizontal divisions for one wavelength x timebase setting

35
Q

Why might components get damaged

A

If the peak supply voltage is greater than the average voltage

36
Q

Describe the difference for current in a series and parallel circuit

A

Series - equal

Parallel - current total = sum of current components

37
Q

Describe the difference in voltage for a series and parallel circuit

A

Series - vtotal = v1 = v2 + v3

Parallel - voltage equal

38
Q

What is resistance

A

The opposition to electrical current

39
Q

When is the resistance largest in a circuit

A

When connected in series

40
Q

What is power

A

The amount of energy transferred per second

41
Q

What is internal resistance

A

Resistance of the electrical source (battery) due to moving charges

42
Q

What is a p-n junction diode

A

An electrical component that is made of two types of semiconductor

43
Q

What type of charges does the n-type lose

A

Negative charge carriers

44
Q

What creates the depletion layer

A

The p-type losing positive charge carriers and the n-type losing negative charge carriers

45
Q

In what direction (relating to the circuit symbol for a p-n diode) can the electrons flow

A

Against the direction of the arrow

46
Q

What band is partially filled in the n-type semiconductor

A

Conduction band