Electricity

Both AC and DC can electrocute a human, with DC requiring higher current, probably more than 300 mA.

Procedures conducted in cardiac-protected areas may involve a direct electrical connection to the heart from a device that is connected to the electrical mains. Such a connection bypasses the relatively high insulation provided by the dry skin. Hence electrical devices must be prevented from allowing even very small faulty electrical currents to flow into the patient (micro-electrocution).

The active wire is connected to the electricity grid and to the electrical device. So the on switch must be able to interrupt this supply. The fuse also is on the active wire so that it “melts” if the current passing through it is above its set value.

3 cm ÷ 2 cm/mV = 1.5 mV.

The earth wire allows current to flow to earth rather than through a person touching the case. In addition, the fuse should melt almost immediately.

Choice B refers to electrical resistance. Choice C refers to the current in amperes (1A =1C/s). Choice D refers to power (P = A/s).

The current is large and is applied to the outside of body to bare skin.

The charge carriers are ions (sometimes called electrolytes); they may have a positive or a negative charge.

The ECG records the voltage produced by the heart muscle measured at the body surface.

Dry human skin presents greater resistance to current flow than damp skin.