Explanation
Because there is no special attractive force that keeps a person stuck with a high power line. The actual reason is that a current of the order of 0.05 A or even less is enough to bring disorder in our nervous system. As a result of it, the affected person may lose temporarily his ability to exercise his nervous control to get himself free from the high power line.
It is quite clear that in a battery circuit, the point of lowest potential is the negative terminal of the battery and the current flows from higher potential to lower potential.
The temperature co-efficient of resistance for metal is positive and that for semiconductor is negative.
In metals free electrons (negative charge) arc charge carriers while in P-type semiconductors, holes (positive charge) are majority charge earners.
It is clear that electrons move in all directions haphazardly in metals. When an electric field is applied, each free electron acquire a drift velocity. There is a net flow of charge, which constitute current.
In the absence of electric field this is impossible and hence, there is no current.
The metallic body of the electrical appliances is connected to the third pin which is connected to the earth. This is a safety precaution and avoids eventual electric shock. By doing this the extra charge flowing through the metallic body is passed to earth and avoid shocks. There is nothing such as reducing the heating of connecting wires by three pin connections.
On increasing temperature of wire the kinetic energy of free electrons increase and so they collide more rapidly with each other and hence their drift velocity decreases. Also when temperature increases, resistivity increases and resistivity is inversely proportional to conductivity of material.
In a conductor there are large number of free electrons. When we close the circuit, the electric field is established instantly with the speed of electromagnetic wave which causes electrons to drift at every portion of the circuit. Due to which the current is set up in the entire circuit instantly. The current which is set up does not wait for the electrons flow from one end of the conductor to the another end. It is due to this reason, the electric bulb glows immediately when switch is on.
The resistance of the galvanometer is fixed. In meter bridge experiments, to protect the galvanometer from a high current, high resistance is connected to the galvanometer in order to protect it from damage.
If either the e.m.f. of the driver cell or potential difference across the whole potentiometer wire is lesser than the e.m.f. of the experimental cell, then balance point will not obtained.
Here assertion and reason both are correct hut the reason is not the correct explanation of assertion.
Wire AB is uniform so current through wire AB at every across section will be same. hence current density J(= i/A) at every point of the wire will be same.
Resistivity of a material is its intrinsic property and is constant at particular temperature. Resistivity does not depend upon shape.
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