Electrical safety Flashcards
1
Q
In micro shock
the current is too small to be harmful
A
False
2
Q
In micro shock
The frequency of the current is not important
A
False
3
Q
In micro shock
The right ventricle is more sensitive than the left
A
True
4
Q
In micro shock
the current must be greater than 100uA
A
True
5
Q
In micro shock
The current may induce asystole
A
False
6
Q
In electric shock
The current is too small to be harmful
A
False
7
Q
In electric shock
The effect depends on the duration of current flow
A
True
8
Q
In electric shock
current mainly affects the flexor muscles
A
False
9
Q
In electric shock
effect depends on the total amount of energy delivered
A
True
10
Q
In electric shock
electrons flow through the body
A
False
11
Q
The electricity supply to an operating theatre
Is a three phase supply
A
False
12
Q
The electricity supply to an operating theatre
consists of live, neautral and earth wires
A
False
13
Q
The electricity supply to an operating theatre
Has a voltage of approx 240V
A
True
14
Q
The electricity supply to an operating theatre
Has an Earth connection from the substation
A
False
15
Q
The electricity supply to an operating theatre
Varies sinusoidally at 50Hz
A
True
16
Q
Electrostatic interferance from a piece of equipment:
Requires a current to flow in the power wires
A
False
17
Q
Electrostatic interferance from a piece of equipment:
Is easily prevented by using screened cable
A
True
18
Q
Electrostatic interferance from a piece of equipment:
Is reduced by insulating the signal leads
A
False
19
Q
Electrostatic interferance from a piece of equipment:
is minimised at high frequencies
A
False
20
Q
Electrostatic interferance from a piece of equipment:
Is halved by doubling the separation between signal and power leads
A
True
21
Q
Electromagnetic interference:
Requires the source of the interference to be drawing current
A
True
22
Q
Electromagnetic interference:
with an ECG monitor can be prevented by using screened leads
A
False
23
Q
Electromagnetic interference:
Is halved by doubling the separation between signal and power leads
A
False
24
Q
Electromagnetic interference:
does not affect battery powered equipment
A
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.
