Read before you solve · 3 min
Read Pulsed Beams: Duty Cycle, Average Current and Power
A pulsed beam has a large current only during a small fraction of each cycle. Separate peak quantities from time averages using the duty cycle.
NSEP · Electricity · 1 linked question · 100% coverage
Know this first
Electricity questions depend on identifying charge, a conducting path and the condition that controls current or magnetic effect.
Current · Flow of electric chargeCircuit · A complete conducting loopResistance · Opposition to current
Study deeper: NCERT Physics · Electricity
See it
Separate charge, current and the path between them
Charge
Path
Current
Charge is a property · current needs a conducting path
Charge is a property; current needs a conducting path. Decide first whether the question concerns charging, resistance, current or earthing.
Find the duty cycle
D = pulse duration / repetition period
The average current
I_avg = D I_peak when the current is constant during each pulse and zero otherwise
Use the right power
Instantaneous beam power during a pulse
P_peak = I_peak V, or I_peak times energy per unit charge
Average power is D P_peak.
Keep times in one unit
Nanoseconds and milliseconds create factors of 10⁶. Convert both before forming the ratio.
OlympIQ exam lens
- ✓Calculate duty cycle first.
- ✓Keep peak and average quantities separate.
- ✓Convert pulse width and period to the same unit.
OlympIQ trap
Using the peak current directly for average power overestimates power by the inverse of the duty cycle.
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