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Flashcards in Electrical safety Deck (134)
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1

In micro shock
the current is too small to be harmful

False

2

In micro shock
The frequency of the current is not important

False

3

In micro shock
The right ventricle is more sensitive than the left

True

4

In micro shock
the current must be greater than 100uA

True

5

In micro shock
The current may induce asystole

False

6

In electric shock
The current is too small to be harmful

False

7

In electric shock
The effect depends on the duration of current flow

True

8

In electric shock
current mainly affects the flexor muscles

False

9

In electric shock
effect depends on the total amount of energy delivered

True

10

In electric shock
electrons flow through the body

False

11

The electricity supply to an operating theatre
Is a three phase supply

False

12

The electricity supply to an operating theatre
consists of live, neautral and earth wires

False

13

The electricity supply to an operating theatre
Has a voltage of approx 240V

True

14

The electricity supply to an operating theatre
Has an Earth connection from the substation

False

15

The electricity supply to an operating theatre
Varies sinusoidally at 50Hz

True

16

Electrostatic interferance from a piece of equipment:
Requires a current to flow in the power wires

False

17

Electrostatic interferance from a piece of equipment:
Is easily prevented by using screened cable

True

18

Electrostatic interferance from a piece of equipment:
Is reduced by insulating the signal leads

False

19

Electrostatic interferance from a piece of equipment:
is minimised at high frequencies

False

20

Electrostatic interferance from a piece of equipment:
Is halved by doubling the separation between signal and power leads

True

21

Electromagnetic interference:
Requires the source of the interference to be drawing current

True

22

Electromagnetic interference:
with an ECG monitor can be prevented by using screened leads

False

23

Electromagnetic interference:
Is halved by doubling the separation between signal and power leads

False

24

Electromagnetic interference:
does not affect battery powered equipment

False

25

Electromagnetic interference:
May be caused by a transformer

True

26

Requirements of an earth connection:
Resistance must be less than 0.5 ohm

False

27

Requirements of an earth connection:
Leakage current must be less than 0.5mA (type 1 equipment)

True

28

Requirements of an earth connection:
Its connection at the substation must be tested regularly

False

29

Requirements of an earth connection:
Must be capable of carrying a current of 25A

True

30

Requirements of an earth connection:
Surge test must be performed at 240V

False

31

The star point:
Is the Earth connection at the electrical substation

True

32

The star point:
Is connected to the neutral wire at the electrical substation

True

33

The star point:
Carries electric current back to the power station

False

34

The star point:
Protects the user from the effects of a lightening strike

True

35

The star point:
is not used in a three phase electricity supply

True

36

An earth free supply:
Increases electrical safety

True

37

An earth free supply:
Provides reduced protection from electric shock

False

38

An earth free supply:
Has line and neutral connections

False

39

An earth free supply:
is required for type II equipment

False

40

An earth free supply:
removes the need for a local earth connection

False

41

The line isolation monitor:
Is required by an earth free supply

True

42

The line isolation monitor:
Generates an alarm if too much current is drawn

False

43

The line isolation monitor:
switches off the supply when an electric shock occurs

False

44

The line isolation monitor:
chesck that more than one phase are not connected together

False

45

When considering electricity:
Electrons move at lose to the speed of light

False

46

When considering electricity:
alternating current has a mean amplitude of zero

True

47

When considering electricity:
For a single phase mains supply the peak voltage is plus minus 250V

False

48

When considering electricity:
direct current is easier to switch than alternating current

False

49

When considering electricity:
current can be dissipated by and earth connection

False

50

In an electrical transformer
The efficiency is approx 60%

False

51

In an electrical transformer
Electrons are transferred between its primary and secondary windings

False

52

In an electrical transformer
changing the turns ratio can increase or decrease the output voltage

True

53

In an electrical transformer
When voltage is halved, the maximum current available is halved

False

54

In an electrical transformer
An earth connection increases efficiency

False

55

Electrical burns:
Are caused by direct current

True

56

Electrical burns:
are concentrated in deep tissues

False

57

Electrical burns:
The size depends on the voltage applied to the tissues

True

58

Electrical burns:
depend upon the size of the current passed

True

59

Electrical burns:
Only occur if the frequency is less than 100KHz

False

60

Electrical skin resistance to direct current defibrillation
decreases as paddle surface increases

True

61

Electrical skin resistance to direct current defibrillation
increases when electrode jelly is applied to the paddles

False

62

Electrical skin resistance to direct current defibrillation
decreases as the energy (watt-seconds) delivered increases

True

63

Electrical skin resistance to direct current defibrillation
increases as the number of shocks increases

False

64

Electrical skin resistance to direct current defibrillation
decreases with an increase in paddle pressure

True

65

Direct current:
flows in one direction

True

66

Direct current:
is constant in magnitude

False

67

Direct current:
Can be produced from alternating current

True

68

Direct current:
Is not harmful to the tissues

False

69

Direct current:
Will cause electrostatic interference

False

70

When considering the classification of electrical equipment:
Type II apparatus requires an earth connection

False

71

When considering the classification of electrical equipment:
The maximum earth leakage for type B(F) equipment is 500uA

True

72

When considering the classification of electrical equipment:
Type I equipment is internally powered

False

73

When considering the classification of electrical equipment:
For type C(F) equipment the (F) signifies Earth fre

False

74

When considering the classification of electrical equipment:
Type III equipment may be used whilst charging

False

75

The fuse in the electrical supply to medical equipment:
should be replaced after 1000 hours service

False

76

The fuse in the electrical supply to medical equipment:
should be of the quick blow type

False

77

The fuse in the electrical supply to medical equipment:
Provides protection from electric shock

True

78

The fuse in the electrical supply to medical equipment:
If placed in the neutral wire enhances electrical safety

False

79

The fuse in the electrical supply to medical equipment:
Can be replaced by an earth leakage circuit breaker (RCCD)

False

80

When considering the electrical supply to medical apparatus:
The local earth wire is brown

False

81

When considering the electrical supply to medical apparatus:
the line wire is red

False

82

When considering the electrical supply to medical apparatus:
The fuse should be chosen to limit leakage current to a safe value

False

83

When considering the electrical supply to medical apparatus:
2 pin plugs avoid the risk of earth leakage

False

84

When considering the electrical supply to medical apparatus:
Use of an extension lead compromises electrical safety

True

85

Type III apparatus:
Require three wires, line, neutral and earth

False

86

Type III apparatus:
the earth leakage current must not exceed o.5mA

False

87

Type III apparatus:
must not be directly connected to a patient

False

88

Type III apparatus:
Can not act as the source of leakage current to a patient

True

89

Type III apparatus:
must have a fuse of less than 1Amp

False

90

The following statements are correct regarding basic electrical quantities and units
the coulomb is a unit of electrical charge equivalent to 6.24 x 10^18

True

91

The following statements are correct regarding basic electrical quantities and units
the coulomb is a base SI unit

False

92

The following statements are correct regarding basic electrical quantities and units
A 3 kW electrical appliance (running on UK mains voltage) would require a 5 amp fuse

False

93

The following statements are correct regarding basic electrical quantities and units
The definition of 1 ampere is the flow of 1 coulomb of charge per second through any crossdirectional area of the conductor

True

94

The following statements are correct regarding basic electrical quantities and units
The resistance of a conductor is a constant value that is not influenced by other factors

False

95

The following statements are correct regarding capacitors and their capacitance:
Capacitors used in defibrillators typically have a capacitance of breater than or equal to 1 farad

False

96

The following statements are correct regarding capacitors and their capacitance:
increasing the distance between the plates of a capacitor increases its capacitance

False

97

The following statements are correct regarding capacitors and their capacitance:
the introduction of a dielectric between the plates increases the capacitance

True

98

The following statements are correct regarding capacitors and their capacitance:
The stored energy of a capacitor is given by the formula E=1/2QV^2

False

99

The following statements are correct regarding capacitors and their capacitance:
Capacitors can be directly charged using alternating current

False

100

An earth free supply (or floating circuit):
Increases electrical safety

True. The supply is not earth referenced. The isolating transformer means that the 240 V supply is no longer connected to the substation, current can therefore not flow through you, via the ground to complete the circuit.

101

An earth free supply (or floating circuit):
Provides reduced protection from electric shock

False. An earth free supply increases protection from electrical shock.

102

An earth free supply (or floating circuit):
Has live and neutral connections

False. Since neither supply wire is connected to ground at the substation there is no 'neutral' wire.

103

An earth free supply (or floating circuit):
Is required for Type II equipment

False. An earth free supply is not required by Type II equipment.

104

An earth free supply (or floating circuit):
Requires a line isolation monitor

True. An earth free supply does require a line isolation monitor to warn you if a fault has compromised safety of the system.

105

Concerning electrical safety:
Ohm's law states that resistance is inversely proportional to current for a given voltage

True

106

Concerning electrical safety:
Wet skin increases the likelihood of electrical shock from faulty equipment

True. Moisture reduces the impedance of skin, increasing the current that flows for a given voltage, and therefore increases the likelihood of electrical shock from faulty equipment.

107

Concerning electrical safety:
Class 1 equipment reduces the risk of electrical shock by providing a low resistance earthed path through which leakage currents may flow

True. Class 1 equipment reduces the risk of electrical shock by providing a low resistance earthed path through which leakage currents may flow.

108

Concerning electrical safety:
The no-let-go threshold occurs at
5 mA

False. The no-let-go threshold is the current at which the strength of the flexor muscle contraction (which is stronger than the extensors') would prevent you from letting go of a live wire. This threshold occurs at about 15 mA.

109

Concerning electrical safety:
Microshock can occur at currents of
20 μA

False. Microshock is unlikely to occur below 44 μA

110

Concerning electrical safety:
All class 1 and 2 equipment is earthed

False. Class 1 equipment standards require that all components with which the user may come into contact are earthed. Class 2 equipment is not earthed, but is 'double insulated'.

111

Concerning electrical safety:
UK mains supply has a peak voltage of 240 volts

False. 240 V is the average (actually the 'root mean square') voltage. The voltage oscillates between +/- 340 V.

112

Concerning electrical safety:
A current of 100 mA passing across the myocardium is often sufficient to induce ventricular fibrillation

True. A current of near 100 mA passing across the myocardium is often sufficient to induce ventricular fibrillation.

113

Concerning electrical safety:
An earth lead eliminates the chance of electrical shock from electrical apparatus

False. The amounts of leakage current passing through the earth wire and an individual in contact with a faulty piece of apparatus is proportional to their resistances.

114

Concerning electrical safety:
A typical medical infusion pump is rated 'BF', i.e. suitable for connection to the body

False. Typical medical infusion pumps are rated 'CF', so they are suitable for direct connection to the heart, because they may be connected via a column of electrolyte solution to the right atrium.

115

Regarding the classification of electrical equipment:
Type II apparatus requires an earth connection

False. Double insulated apparatus has two physical barriers between the electrically applied part (the part of the apparatus connected to the mains) and the user.

116

Regarding the classification of electrical equipment:
The maximum earth leakage current for type BF equipment is 500 μA

True. In BF Type I equipment, the leakage current must not exceed
0.5 mA (500 μA).

117

Regarding the classification of electrical equipment:
Type I equipment is internally powered

False. Type III equipment is internally powered.

118

Regarding the classification of electrical equipment:
For type CF equipment the 'F' signifies earth free

False. The F suffix states that the patient applied part is 'floating', i.e. it is electrically isolated from the rest of the apparatus.

119

Regarding the classification of electrical equipment:
Type III equipment may be used whilst charging

False. Type III equipment is 'internally powered', if connected to an external power supply whilst charging it is no longer internally powered and the classification would change to that of the charger.

120

Type III apparatus:
Requires three wires: live, neutral and earth

False. Type III apparatus is internally powered.

121

Type III apparatus:
The earth leakage current must not exceed 0.5 mA (500 μA)

False. Type III apparatus has no mains connection,0.5 mA is the maximum allowable leakage from Type 1 BF equipment.

122

Type III apparatus:
Must not be directly connected to a patient

False. Type III apparatus can be directly connected to a patient, e.g. an internally (battery) powered nerve stimulator.

123

Type III apparatus:
Cannot act as the source of leakage current to a patient

True. Type III apparatus has no mains connection.

124

Type III apparatus:
Must have a fuse of less than 1 A

False. Type III apparatus has no mains connection.

125

Which of the following statements are true of diathermy?
It uses high frequency alternating current in the order of 5 MHz

False. Diathermy uses uses high frequency alternating current up to 1 MHz.

126

Which of the following statements are true of diathermy?
Current density at the diathermy tip determines the degree of burning

True. Current density at the diathermy tip determines the degree of burning.

127

Which of the following statements are true of diathermy?
In monopolar diathermy, the same high frequency current flows through the diathermy tip as the return plate

True. In monopolar diathermy, the same high frequency current flows through the diathermy tip as the return plate.

128

Which of the following statements are true of diathermy?
Bipolar diathermy does not need a separate skin electrode

True. Bipolar diathermy does not need a separate skin electrode because the forceps act as both tip and return plate.

129

Which of the following statements are true of diathermy?
The diathermy cannot pass current if the return plate is incorrectly applied

False. Current will still flow to a poorly applied ground plate. The reduced surface area increases current density which may result in burns.

130

Surgical diathermy:
Has a lower frequency when used for coagulation than when used for cutting

True. High frequency continuous oscillation is used for cutting, while bursts of lower frequency are preferred for coagulation.

131

Surgical diathermy:
Has a higher voltage when used for coagulation than when used for cutting

True. Coagulation uses voltages up to 9 kV, whilst cutting uses voltages up to 1 kV.

132

Surgical diathermy:
Should never be used in patients with pacemakers

False. Bipolar diathermy relies on the passage of current between two electrodes close together. This minimizes the passage of current through the body and so avoids the risk of problems with pacemakers.

133

Surgical diathermy:
May cause explosions even when non-flammable anaesthetic agents are in use

True. Flammable anaesthetic agents are not the only combustible gases in theatre, and fires have been reported from surgical cleaning agents as well as explosions from gas within the bowel.

134

Surgical diathermy:
Must always be earthed

False. Bipolar diathermy is not earthed. Unipolar diathermy is earthed but uses an isolating capacitor to restrict the flow of mains frequency current.