Q 14. As the current in the filament varies through the ac cycle, the power dissipated in the filament varies and the temperature of the filament (which was raised due to power dissipation) varies. If this happens slow enough, your eye is able to detect this variation (or flicker) but a low frequency is required. The human eye cannot detect the 60 Hz variation which is always present because it is too fast.
Q 10. Electrical appliances in a home are connected in parallel across the 120 V power line. If you add a second lamp to the circuit which is connected in parallel with the first lamp, the total resistance of the parallel combination will always be smaller than that of the firxt lamp alone. This is the inevitable result of summing 1/R rather than R.
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