Electricity

Using Ohm’s law: V = I × R, so R = V ÷ I and realising that 100 mA = 0.1A, putting in the numbers gives: R = 240 × 0.1 = 2400 ohms

Macro-electrocution refers to electrocution by a relatively large current that is applied to the skin surface.

Ohm’s law: V = I × R, so I = V ÷ R. Choice C also produces the correct answer for current but does not use Ohm’s law.

An ion will have a positive charge when it has lost one or more electrons. Hence it will have more protons in its nucleus than electrons in the orbitals.

ECG electrodes are applied to the patient’s skin, so do not bypass the barrier to electric current flow that is the skin. Consequently, the protection must be against macro-electrocution. A body-protected area is required. “Double insulated” is a term that is applied to domestic appliances with an external plastic structure.

Ohm’s law as stated is: I = V ÷ R putting in the numbers gives: I = V ÷ R = 240 ÷ 80,000 = 0.003A = 3 mA.

Procedures conducted in body-protected areas do not involve a direct electrical connection to the heart. Hence only faults that allow relatively large currents can produce electrocution (macro-electrocution).

Microshock refers to electrocution by a current above about 100 μA if delivered by a conductor that has penetrated the skin. Currents less than this are probably not fatal. If the current greater than 100 mA is applied to the exterior of the skin, it is called microshock. Choice D is referring to external defibrillation.

(I may be picking a fight here) Transformers (which change voltage of electrical power) and circuit breakers are dramatically less expensive for AC than for DC.

Voltage is the unit of potential difference and ohms is the unit of resistance.