1. A. The SI unit for current is the ampere.
2. C. The unit for resistance = ohm.
3. B. EMF is measured in volts.
4. B. Electric current is the flow of charged particles, i.e. electrons.
5. B or C. All other answers are metals.
6. C. The dimensions of a material don't affect its resistance.
7. D. Ohm's law: current = voltage / resistance, 12/4 = 3.
8. B. Batteries transform chemical energy into electrical energy.
9. A. Metals are generally good conductors.
Answer:
Mass of the box = 0.9433 kg
Explanation:
Mass of racket-ball
= 0.00427 kg
Velocity of racket-ball before collision
= 22.3 m/s
Velocity of racket-ball after collision with box
= -11.5 m/s
[Since ball is bouncing back, so velocity is taken negative.]
Velocity of the box before collision
= 0 m/s
<em>[Since the box is stationary, so velocity is taken zero]</em>
Velocity of box moving forward after collision
= 1.53 m/s
To find the mas of the box
.
By law of conservation of momentum we have:
Momentum before collision = Momentum after collision
This can be written as:


We can plugin the given value to find 


Adding both sides by 0.4911


Dividing both sides by 1.53.


∴
kg
Mass of the box = 0.9433 kg (Answer)
The resistance is increased when more and more bulbs are added to the circuit.