Question

How many electrons will pass a fixed point in a 2000 Watt heater in 1 minute if the applied voltages are 240 V?

Answer 1

Answer:

• Number of electrons passing through the fixed point = 3.125 × 10²¹ electrons.

Explanation:

Given:

• Power rating of heater, P = 200 W
• time, t = 1 min = 60 sec
• Potential difference, V = 240 V

To find:

• Number of electrons passing a fixed point, n =?

Knowledge required:

• Relation between Power, energy and time

       E = P × t

• Relation between work done, charge and potential difference

        V = W / Q

• Number of electrons containing 1 Coulomb of charge

        1 coulomb of charge contain 6.25 × 10¹⁸ electrons.

[ Where E is energy, P is power, t is time, W is work done, V is potential difference and Q is charge]

Solution:

Let, Energy consumed by Heater be E

then, Using formula

→ E = P × t

→ E = (2000) × (60)

→ E = 120000 J

 Now, Since Energy consumed is equivalent to the work done therefore,

Energy consumed, E = Work done, W = 120000 J

Let, charge through fixed point be Q

Now, Using formula

→ V = W / Q

→ Q = W / V

→ Q = 120000 / 240

→ Q = 500 C

Now,

Let, number of electrons through the fixed point be n

Since, there are 6.25 × 10¹⁸ electrons in 1 Coulomb of charge

therefore,

→ n = Q × electrons in 1 C charge

→ n = 500 × 6.25 × 10¹⁸

→ n = 3.125 × 10²¹ electrons

Therefore,

• A total of 3.125 × 10²¹ electrons will pass through the fixed point.

Answer 2

Answer:

Because the resistance of the heater element would change with its temperature, it would be impossible to answer the question accurately; only an approximate answer could be given. Also, I would like to know the reason for the question. Do you really want to operate the heater on a lower voltage? If so, why? 200 volts is not even a standard voltage.

None of the questions in this series seem intended to provide helpful or practical information. Rather, it looks as though someone has spent time devising abstract questions of a type which one might find on a high school physics test. But even for a physics test, some of the questions would make absolutely no sense the reason being that the information provided is insufficient to provide a definitive answer.

Some of the questions on quora are good because they lead to interesting conversations and an exchange of different points of view, but questions like the ones in this series seem useless.

Explanation:

Hope it helps!