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Module 3: Electrical Fundamentals (B1) :!: > 3.7: Resistance/Resistor > Flashcards

3.7: Resistance/Resistor Flashcards

1
Q
  1. A carbon resistor consists of the following code: Band 1 Red, Band 2 Green,
    Band 3 Blue. What is the value and tolerance of the resistor?
    (a) 250KΩ and 10% tolerance.
    (b) 25MΩ and 20% tolerance.
    (c) 250MΩ and 5% tolerance.
A

(b) 25MΩ and 20% tolerance.

Black boys r*** our young girls but Violet gives willingly - note
1st band = 1st digit, 2nd band = 2nd digit, 3rd band is multiplier and 4th is tolerance
Where Gold = +-5% and silver is +-10%

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2
Q
  1. Potentiometers are used in electrical circuits to vary the:
    (a) amount of current flow in the circuit
    (b) the amount of voltage applied to the circuit
    (c) neither of the above
A

(b) the amount of voltage applied to the circuit

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3
Q
  1. If a circuit consisting of a 8 ohm, 15 ohm, 25 ohm and 35 ohm resistors connected
    in series. The total resistance of the circuit is;
    (a) 53 ohms,
    (b) 73ohms.
    (c) 83 ohms
A

(c) 83 ohms

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4
Q
  1. If three resistors of 3 ohms, 4 ohms and 5 ohms are connected in series to a 24V
    supply, how much voltage would appear across the 3 ohm resistor
    (a) 24V
    (b) 6V
    (c) 3V
A

(b) 6V

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5
Q
  1. A carbon resistor consist of the following code, Band1 Orange, Band 2 Yellow
    Band 3 orange and Band 4 Silver. What is the value and tolerance of the resistor?
    (a) 3400 Ω and tolerance of 1%
    (b) 34000 Ω and tolerance of 5 %
    (c) 34KΩ and tolerance of 10%
A

(c) 34KΩ and tolerance of 10%

Black boys r*** Our young girls but violet gives willingly
1st band = 1st digit, 2nd band = 2nd digit, 3rd band = multiplier and 4th band is tolerance
Where Gold = +-5% and silver is +-10%

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6
Q

What is the voltage V when the switch is closed?
2.5 V
6.5 V
97.5 V
100.0 V

A

97.5 V

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7
Q
  1. What are the values of the Output Voltage and the Internal Resistance of this twocell battery?
    (a) 6 Volts and 1 ohm.
    (b) 6 Volts and 2 ohms.
    (c) 6 volts and 0.5 ohms.
A

(c) 6 volts and 0.5 ohms.

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8
Q
  1. If the cross-sectional area of a conductor is reduced to half, its effective resistance
    will:
    (a) Remain the same
    (b) Double
    (c) Halve
A

(b) Double

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9
Q
  1. If the cross-sectional area of a conductor is doubled, its effective resistance will:
    (a) Remain the same
    (b) Double
    (c) halve
A

(c) halve

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10
Q
  1. Replacing an Aluminum wire with a copper wire of the same guage (size) will
    cause the circuit’s resistance to:
    (a) Increase
    (b) Decrease
    (c) Remain the same
A

(b) Decrease

'’Copper is a better conductor compared to aluminium. Aluminium has 61% of the conductivity of copper, but it has only 30% of the weight of copper. That means that a bare wire of alumium weighs half as much as a bare wire of copper that has the same electrical resistance.’’

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11
Q
  1. Replacing an Gold wire with a copper wire of the same guage (size) will cause
    the circuit’s resistance to:
    (a) Increase
    (b) Decrease
    (c) Remain the same
A

(b) Decrease

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12
Q

Rank the following in order from most conductive to least (all still top 5 most conductive but relative to each other)
Gold, Copper, Silver and Aluminium

A
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13
Q
  1. Three resistors with values of 120 ohms, 60 ohms, and 40 ohms are connected in
    parallel. What is the equivalent resistance of the circuit?
    (a) 10 Ω
    (b) 20 Ω
    (c) 30 Ω
    (d) 40 Ω
A

(b) 20 Ω

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14
Q
  1. Two resistors with values of 90 ohms and 45 ohms are connected in parallel.
    What is the equivalent resistance of the circuit?
    (a) 10 Ω
    (b) 20 Ω
    (c) 30 Ω
    (d) 40 Ω
A

(c) 30 Ω

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15
Q
  1. What is the value of Es?
    (a) 336 V
    (b) 300 V
    (c) 240 V
    (d) 120 V
A

(d) 120 V

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16
Q
  1. .What is the value of the total resistance?
    (a) 3.6Ω
    (b) 15Ω
    (c) 34Ω
    (d) 40Ω
A

(b) 15Ω

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17
Q
  1. What is the total voltage drop across R 3?
    (a) 8 V
    (b) 12 V
    (c) 18 V
    (d) 30 V
A

(b) 12 V

Remember: The voltage drop across the parallel resistors is a fixed value and the same for each despite their different resistance values as is potential difference betweent the two sides. However the current is not, 2 different values of current will flow through each resistor

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18
Q
  1. The opposition to AC or DC current flow that dissipates power is called ?
    (a) Reactance
    (b) Reluctance
    (c) Resistance
A

(c) Resistance

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19
Q
  1. A resistor with a positive temperature coefficient of resistance, means that as the
    temperature increases, it’s resistance:
    (a) Decreases
    (b) Increases
    (c) Multiplies by 5
A

(b) Increases

Positive Temperature Coefficient = Resistance increases with increasing temperature
Negative Temperature Coefficient = Resistance decreases with increasing temperature

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20
Q
  1. The resistance of a conductor with a negative temperature coefficient of
    resistance will:
    (a) Decrease with increased temperature
    (b) Increase with increased temperature
    (c) Fall with increased temperature
A

(a) Decrease with increased temperature

Positive Temperature Coefficient = Resistance increases as temperature increases
Negative Temperature Coefficient = Resistance decreases as temperature increases

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21
Q
  1. Conductance is the inverse value of which characteristic?
    (a) Inductance
    (b) Resistance
    (c) Capacitance
A

(b) Resistance

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22
Q
  1. Rheostats are used in electrical circuits to vary the:
    (a) amount of current flow in the circuit
    (b) the amount of voltage applied to the circuit
    (c) neither of the above
A

(a) amount of current flow in the circuit

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23
Q
  1. Maximum power is transferred from a source to a load when the value of the load
    resistance is of what value when compared to the source resistance?
    (a) Equal
    (b) Twice
    (c) One-half
    (d) Several times
A

(a) Equal

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24
Q
  1. . A circuit consists of three resistors connected in parallel. R1 = 30 ohms, R2 = 15
    ohms, and R 3 = 10 ohms. If the current through R2 = 4 amperes, what is the total
    source voltage?
    (a) 20 V
    (b) 60 V
    (c) 120 V
    (d) 220 V
A

(b) 60 V

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25
Q
  1. The tolerance of a resistor is normally shown through which method?
    (a) Using the first colour band on the resistor
    (b) Writing it on the resistor
    (c) Using the fourth colour band on a resistor
A

(c) Using the fourth colour band on a resistor

Gold is +-5%, silver is +-10%

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26
Q
  1. The tolerance of a resistor is normally shown through which method?
    (a) Using the first colour band on the resistor
    (b) Using the fifth colour band on a resistor
    (c) Using the fourth colour band on a resistor
A

(c) Using the fourth colour band on a resistor

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27
Q
  1. A wheatstone bridge circuit is constructed of:
    (a) 3 fixed and 1 variable resistor
    (b) 4 fixed resistors
    (c) 4 variable resistors
A

(a) 3 fixed and 1 variable resistor

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28
Q
  1. The wire in a wire wound resistor is wound around a:
    (a) metal base
    (b) porcelain base
    (c) silicon base
A

(b) porcelain base

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29
Q
  1. A 24-volt source is required to furnish 48 watts to a parallel circuit consisting of
    four resistors of equal value. What is the voltage drop across each resistor?
    (a) 12 volts
    (b) 24 volts
    (c) 3 volts
A

(b) 24 volts

In Parallel = 24 V

Cross Check 48 = 24 X 24/R Hence R = 12 hence each resistance 48 Ohm I = V/R = 1/2A
.5 X 48 = 24 volts as above.

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30
Q
A

(a) 2.5 V

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31
Q
  1. An EMF of 24 volts is applied to a closed circuit of total resistance 2KΩ. the
    current in the circuit is?
    a. 12 A
    b. 12 mA
    c. 48 kA
A

b. 12 mA

32
Q
A

c. 100 Ω

Wheatstone network uses a Galvanometer and can measure the resistance of an unkown piece of equipment. If wheatstone bridge is balanced, no current will flow through Galvanometer. This reduces circuit to a simple parallel circuit. However for this to occur the ratios must be the same, i.e if one side is 1 ohm and then 7 ohm, the other side must be 5 ohm and 35 ohm. The ratios must be the same.

Thus, by making one resistor a variable resistor, this can be adjusted and when the galvanometer reads 0, the proportions must be balanced and so can know resistance value.

33
Q

Max power transfer is when source and load resistance are ___________

A

Equal

34
Q

Potentiometer varys _______
Rheostat varys _______

A

Potentiometer varys voltage
Rheostat varys large current

35
Q

What is the formula for resistivity?

A

Where rho is the static resistivity (ohm-m or ohm meter - SI unit of resistivity)
L is the length of the piece of material (m)
and A is the cross-sectional area (m^2)

36
Q

Question Number. 1. The resistance of a material is.
Option A. independent of the material type.
Option B. the same as its conductance.
Option C. the reciprocal of its conductance.

A

Option C. the reciprocal of its conductance.

37
Q

Question Number. 2. Resistance is measured using what unit of temperature?.
Option A. Absolute.
Option B. Centigrade.
Option C. Fahrenheit.

A

Option A. Absolute.

38
Q

Question Number. 3. A resistor has 4 bands on it coloured blue, yellow, yellow, gold. It’s value is. Option A. 640 kΩ ± 5%.
Option B. 6.4 mΩ ± 10%.
Option C. 64 kΩ ± 5%.

A

Option A. 640 kΩ ± 5%.

39
Q

Question Number. 4. The electron flow through a conductor will be decreased the most if the cross sectional area.
Option A. is decreased and the length is increased.
Option B. and the length are both decreased.
Option C. and the length are both increased.

A

Option A. is decreased and the length is increased.

40
Q

Question Number. 5. Small resistors too small or mis-shapen for the application of colour are marked instead using.
Option A. an abbreviated resistance value.
Option B. a letter code.
Option C. a dot code.

A

Option B. a letter code.

41
Q

Question Number. 6. Total resistance in a parallel resistor circuit, of R1 and R2 is. Option A. RT = 1/R1 + 1/R2.
Option B. 1/RT = (R1 * R2) ÷ (R1 + R2).
Option C. 1/RT = 1/R1 + 1/R2.

A

Option C. 1/RT = 1/R1 + 1/R2.

42
Q

Question Number. 7. If the resistance of a resistor which is in series with two other resistors is doubled.
Option A. the current in that resistance is doubled.
Option B. the volts drop across that resistor increases.
Option C. the current in that resistance is halved.

A

Option B. the volts drop across that resistor increases.

Note: The current will reduce, but not halved, since it depends on how big the other two resistors are in relation to it. It will however take a greater share of the voltage drop in the circuit

43
Q

Question Number. 9. Potentiometers are used as a.
Option A. variable voltage source.
Option B. variable resistor.
Option C. variable current source

A

Option B. variable resistor.

Note: Potentiometers can by used to vary voltage but are not a ‘source’ of voltage

44
Q

Question Number. 11. In general, increasing the cross sectional area of an electrical cable. Option A. increases its resistance.
Option B. enables it to carry more voltage.
Option C. enables it to carry more current.

A

Option C. enables it to carry more current.

Note: Get the formula for resistance of a cable. If you increase the cross sectional area, its resistance will decrease and it can carry more current. ‘Carrying voltage’ is not technically correct terminology, and besides, any size cable can ‘carry’ any size voltage, but it is the current which will destroy it.

45
Q

Question Number. 12. Six resistors each of 6 ohms would be.
Option A. 1 ohm in series.
Option B. 1 ohm in parallel.
Option C. 36 ohms in parallel.

A

Option B. 1 ohm in parallel.

46
Q

Question Number. 13. A potentiometer varies.
Option A. resistance.
Option B. current.
Option C. voltage

A

Option C. voltage

Note: A potentiometer is basically a variable voltage splitter

47
Q

Question Number. 14. The formula for resistance in series is.
Option A. RT = R1 + R2 + R3 …..Rn.
Option B. RT = R1 * R2 * R3 …..Rn.
Option C. 1/RT = 1/( R1 * R2 * R3 …..Rn).

A

Option A. RT = R1 + R2 + R3 …..Rn.

48
Q

Question Number. 15. What is the combined value of resistances of 4 ohm and 6 ohm connected in parallel?.
Option A. 0.24 ohm.
Option B. 2.4 ohm.
Option C. 24 ohm.

A

Option B. 2.4 ohm.

Note: Resistors in parallel, the total resistance will be less than the smallest (but only slightly less)

49
Q

Question Number. 16. If a number of resistors are connected in parallel, the total resistance is.
Option A. smaller than the lowest.
Option B. the same as the lowest.
Option C. greater than the lowest.

A

Option A. smaller than the lowest.

50
Q

Question Number. 17. The resistance to electrical flow in a wire depends on.
Option A. the diameter, length, material of wire and temperature.
Option B. the material only - copper or aluminium.
Option C. the length and material of the wire only.

A

Option A. the diameter, length, material of wire and temperature.

51
Q

Question Number. 18. When resistors are in parallel the total current is equal to.
Option A. the current through one resistor.
Option B. the sum of the currents.
Option C. the reciprocal of all the currents.

A

Option B. the sum of the currents.

52
Q

Question Number. 19. Which of these will cause the resistance of a conductor to decrease?. Option A. Decrease the length or the cross-sectional area.
Option B. Increase the length or decrease the cross-sectional area.
Option C. Decrease the length or increase the cross-sectional area.

A

Option C. Decrease the length or increase the cross-sectional area.

53
Q

Question Number. 20. If 2 resistors, one red, yellow, black, gold and the other violet, blue, black, silver were replaced by a single resistor. Ignoring tolerance, what would the colour coding be?. Option A. Brown, black, brown.
Option B. Black, brown, black.
Option C. Brown, black, black.

A

Option A. Brown, black, brown.

'’The red/yellow/black resistor is 24 ohms. The violet/blue/black resistor is 76 ohms. Total is 100 ohms. A 100 ohm resistor is brown/black/brown

54
Q

Question Number. 21. A 47 kilohm resistor has the following colour code:.
Option A. Yellow, Violet, Orange.
Option B. Red, Orange, Yellow.
Option C. Orange, Violet, Red.

A

Option A. Yellow, Violet, Orange.

55
Q

Question Number. 23. A 300 ohm resistor would have a colour code of.
Option A. orange, brown, black.
Option B. orange, orange, brown.
Option C. orange, black brown.

A

Option C. orange, black brown.

56
Q

Question Number. 25. In a parallel circuit containing resistors.
Option A. the sum of the voltage drops equals applied voltage.
Option B. the voltage is the same in all parts of the circuit.
Option C. resistance is determined by value of current flow.

A

Option B. the voltage is the same in all parts of the circuit.

Note: In a parallel circuit, the voltage across each resistor is the same

57
Q

Question Number. 26. Five different value resistors all have the same voltage dropped across them. How are the resistors connected?.
Option A. In Series/Parallel.
Option B. In Series.
Option C. In Parallel.

A

Option C. In Parallel.

Note: Resistors in parallel with each other all have the same voltage drop

58
Q

Question Number. 27. Conductance of a circuit is 2 milliMhos. What is its resistance?. Option A. 5000 Ohms.
Option B. 500 Ohms.
Option C. 5 Megohms.

A

Option B. 500 Ohms.

Note: Conductance is the ease at which current flows. It is the inverse of resistance (The unit ‘Mho’ is ‘Ohm’ backwards). Conductance = 2/1000 Mhos. Therefore Resistance = 1000/2 ohms

59
Q

Question Number. 28. When light hits a photodiode, its resistance.
Option A. stays the same.
Option B. increases.
Option C. decreases.

A

Option C. decreases.

Note: Resistance decreases with light intensity

60
Q

Question Number. 29. A 2 Megohm resistor can be written.
Option A. 2M0F.
Option B. 20MF.
Option C. M20F.

A

Option A. 2M0F.

Sometimes the multiplier, like M (for mega), or k (for kilo) or R (for 1) is put in place of the decimal point. The last letter is the tolerance.

61
Q

Question Number. 30. In a Wheatstone bridge at balance the galvanometer reads zero.
Option A. amps.
Option B. ohms.
Option C. volts.

A

Option A. amps.

62
Q

Question Number. 31. The unit for resistivity is the.
Option A. ohms/square meter.
Option B. ohms/meter.
Option C. ohm.meter.

A

Option C. ohm.meter.

63
Q

Question Number. 32. A 47 Kilohm resistor with a 10% tolerance has the following colour code:.
Option A. Yellow, Violet, Orange, Silver.
Option B. Orange, Violet, Red, Gold.
Option C. Red, Orange, Yellow, Silver.

A

Option A. Yellow, Violet, Orange, Silver.

64
Q

Question Number. 33. The total resistance in a circuit is greater than the least resistor. This is true for a.
Option A. series and parallel circuit.
Option B. series circuit only.
Option C. parallel circuit only.

A

Option B. series circuit only.

65
Q

Question Number. 3. A potentiometer has which of the following properties?.
Option A. Wire wound.
Option B. 3 terminals.
Option C. Preset values.

A

Option B. 3 terminals.

66
Q

Question Number. 4. An increase in operating temperature in most electrical devices carrying current results in.
Option A. a decrease in resistance and an increase in current.
Option B. no effect on the resistance and current.
Option C. an increase in resistance and a decrease in current.

A

Option C. an increase in resistance and a decrease in current.

Most conductors have a ‘positive temperature coefficient’. The exceptions are semiconductors

67
Q

Question Number. 5. Copper is an inferior conductor to aluminium when comparing.
Option A. CSA with CSA.
Option B. weight for weight.
Option C. load for load.

A

Option B. weight for weight.

Copper is a better inductor but aluminium is much lighter

68
Q

Question Number. 6. What happens to the resistance of a copper conductor when the temperature increases?.
Option A. It decreases.
Option B. It increases.
Option C. It remains the same.

A

Option B. It increases.

All materials except semiconductors have a positive temperature coefficient

69
Q

Question Number. 7. Carbon has a.
Option A. temperature coefficient of zero.
Option B. positive temperature coefficient.
Option C. negative temperature coefficient.

A

Option C. negative temperature coefficient.

Carbon is a semiconductor, so its resistance reduced with temperature

70
Q

Question Number. 8. The 5th coloured band on a resistor represents the.
Option A. reliability or temperature coefficient.
Option B. tolerance.
Option C. multiplier.

A

Option B. tolerance.

71
Q

Question Number. 9. If the temperature of a pure metal is reduced to absolute zero, its resistance will be.
Option A. unaffected.
Option B. practically zero.
Option C. infinity.

A

Option B. practically zero

72
Q

A potentiometer has ___ connections, a rheostat has only ___

A

A potentiometer has 3 connections, a rheostat has only 2.

73
Q

Question Number. 11. If a resistor is too small or misshapen to fit the colour code bands, how else is it’s value indicated?.
Option A. Dots.
Option B. Number code.
Option C. Letter code.

A

Option C. Letter code.

74
Q

Question Number. 14. Resistors required to carry a comparatively high current and dissipate high power are usually of.
Option A. Wire wound metal type.
Option B. Carbon compound type.
Option C. Wire wound ceramic type.

A

Option C. Wire wound ceramic type.

75
Q

Question Number. 15. A thyristor.
Option A. if energized on, will switch on a circuit.
Option B. has a positive temperature coefficient.
Option C. if energized on, will switch off a circuit.

A

Option A. if energized on, will switch on a circuit.

76
Q

Question Number. 16. The temperature of a pure metal can greatly affect the resistance of it. What temperature scale is used?.
Option A. Absolute.
Option B. Centigrade.
Option C. Fahrenheit.

A

Option A. Absolute.

Module 3: Electrical Fundamentals (B1) :!: (19 decks)

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