Please help in these 4 questions

See the answers below.

Explanation:

1

The data of 100W means power, and the other data of 220V means voltage, that is to say that bulb serves to work at a voltage of 220V100W datum means power.

J means work that is given in Joules [J], we must remember that power is defined as the relationship between work at a certain time, therefore we can determine work by means of the following expression.

where:

P = power [Watt]

W = work [J]

t = time [s]

Now the electric cost.

2

We know that power is defined as the product of voltage by resistance.

where:

P = power [W]

V = voltage [V]

I = current [amp]

3

The voltage can be calculated by means of ohm's law, which tells us that the voltage is equal to the product of resistance by the current.

where:

V = voltage [V]

I = current = 20 [mA] = 0.02 [A]

R = resistance = 20 [kΩ] = 20000 [Ω]

Now replacing:

4

According to the figure we see that when the current is equal to 10 [mA] the voltage is equal to 1 [V]. With these two values, we can use ohm's law and find the value for the resistance.

0.3x0.21x0.08kg=mass 1 sheet

mass 500 = 500xmass 1

volume pile = 0.3x0.2x0.048

density=mass/volume= 500xmass 1/0.3x0.2x0.048

v patient student