Question

0. Are the statements true or false and briefly explain your choice, in words or pictures

1. When three bulbs are put in parallel across a battery, more current leaves the battery than when only one bulb is connected to the same battery.

2. As a sound wave “dies out” (gets quieter), the amplitude, speed and frequency all diminish.

3. The two ends of a permanent magnet have opposite charges.

   1. When three bulbs are put in series across a battery, more current leaves the battery than when only one bulb is connected to the same battery.

   2. You can change the speed of a wave by changing the frequency and/or wavelength.

   3. An electromagnet does not need an iron core.

   4. Because the filament wire of a light bulb has resistance, the current leaving the bulb is less than the current entering the bulb.

Answer 1

1. True. When resistors are connected in parallel across the battery, the equivalent resistance is less and hence the current is more. I = V/R. If resistance of single bulb is R, then equivalent resistance is of 3 bulbs connected in parallel is R/3.

2. False. When sound waves dies out only the amplitude of the sound waves diminishes.

3. False. The two ends of a permanent magnet have opposite (magnetic) poles.

4. False. When resistors are connected in seris across the battery, the equivalent resistance is high and hence the current is less. I = V/R. If resistance of single bulb is R, then equivalent resistance is of 3 bulbs connected in seris is 3R.

5. False. The speed of the wave depends on the nature of the wave (e.g. mechanical or non-mechanical) and the medium in which it travels.

6. It is not necessary to have iron core for electromagnet, however, Iron core will improve the performance.

7. False. Net charge can not be created or destroyed.