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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In which type of current possibility to be released from a shock?
AC
DC
Both
None of above
AC
Quick Summary: AC (Alternating Current) causes muscles to contract and relax at the frequency of the supply (e.g., 50 Hz), which periodically allows the victim's muscles to release the conductor. In contrast, DC (Direct Current) causes continuous, sustained muscular contraction, making it much harder for a person to let go of an energized component.
AC (Alternating Current) causes muscles to contract and relax at the frequency of the supply (e.g., 50 Hz), which periodically allows the victim's muscles to release the conductor. In contrast, DC (Direct Current) causes continuous, sustained muscular contraction, making it much harder for a person to let go of an energized component.
Irelease=f(t) — Current magnitude vs time characteristics for grip release
The human nervous system operates via electrical signals. When an external AC source is applied, the periodic reversal of current at 50Hz causes the muscles to alternate between contraction and partial relaxation. This phenomenon provides brief windows during each cycle where the limb can potentially be withdrawn. DC, having a constant magnitude and direction, triggers a 'lock-on' effect where the flexor muscles remain in a constant state of contraction, preventing voluntary muscle control.
AC current crosses zero twice per cycle, providing momentary release opportunities.
DC current creates a 'clamping' effect due to sustained electrolysis and continuous muscular activation.
The threshold for 'let-go' current is significantly lower for DC than for AC.
Electrical safety protocols emphasize de-energization and use of insulated tools.
AC allows for potential release due to zero-crossings
Easier to interrupt AC circuits using zero-point breaking in switchgear
AC can induce ventricular fibrillation at lower current levels
DC causes deep tissue burns due to continuous current flow
Industrial safety training
Electrical system design and earthing
Personal Protective Equipment (PPE) standards
| Feature | AC | DC |
|---|---|---|
Muscular Effect | Periodic contraction/relaxation | Sustained 'Lock-on' contraction |
The 50Hz frequency used in India is particularly dangerous for the heart but paradoxically allows for muscle release compared to DC.
Option B is incorrect because DC leads to higher probability of involuntary gripping due to constant current polarity.
A is correct — AC provides periodic zero-crossing points that facilitate the release of muscles, whereas DC causes sustained contraction.
In competitive exams, always remember that while AC is generally considered more dangerous for heart rhythm (fibrillation), DC is more dangerous for 'release' capability due to the electrochemical effects on muscle tissues.