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NCERT Solutions Curiosity Chapter 4 –53Section 4.2 Does a Current Carrying Wire Get Hot? — Activity 4.5: Let us observe

Book page 52 Updated on2026-09-05

Q1.
Touch the nichrome wire. What do you feel?
Answer

With the switch still in the OFF position, the nichrome wire feels cool — it is at room temperature, no different from the cardboard or the nails around it.

Why this step matters: this is your reference reading. Unless you know how the wire feels before any current flows, you cannot honestly claim afterwards that the current made it warm. Every good experiment begins by recording the starting condition.
Q2.
Move the switch to ON position for about 30 s and then move it back to OFF. Touch the nichrome wire momentarily (Do not hold the nichrome wire). What difference do you feel?
Answer

Now the wire feels distinctly warm. Repeat the ON–OFF cycle and you get the same result each time, which confirms that the warmth is caused by the current.

Why it happens: the nichrome wire offers resistance to the current passing through it. Because of that resistance, some of the electrical energy is converted into heat energy in the wire, and the temperature of the wire rises. This warming of a conductor when current passes through it is called the heating effect of electric current. Nichrome is chosen for this activity precisely because it offers higher resistance than a copper wire of the same size and length, so the heating is large enough to feel in 30 seconds.
Safety first (from the book, page 53): Do not touch the wire for an extended period to avoid any injuries. Touch it only momentarily, and do not hold the nichrome wire.

How much heat is produced depends on the material, the thickness and the length of the wire, the magnitude of the current, and the duration for which the current flows.

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