Question

Please help in these 4 questions

Answer 1

See the answers below.

Step-by-step 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.

`P=W/t\\`

where:

P = power [Watt]

W = work [J]

t = time [s]

`W=P*t\\W=100*5[hr]*[(3600s)/(1hr) ]\\W=1800000[J] = 1.8[MJ]`

Now the electric cost.

`0.1[kW]*5[hr]*55(LL)/(1kwhr) =27.5[LL]`

2

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

`P=V*I`

where:

P = power [W]

V = voltage [V]

I = current [amp]

`I=P/V\\I=1500/220\\I=6.82[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.

`V =I*R`

where:

V = voltage [V]

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

R = resistance = 20 [kΩ] = 20000 [Ω]

Now replacing:

`V = 0.02*20000\\V = 400 [V]`

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.

`V = I*R\\R = V/I\\R = 1/0.01\\R =100 [ohm]`