Drift Velocity

Q. The force on electrons due to the electric field set up inside a conductor, doesn’t accelerate them on an average because

1. Newton’s second law is not valid inside a conductor
2. Some mysterious force pulls the electrons in the other direction
3. The electrons keep hitting the fixed positive ions and lose their momentum
4. Electrical force can never accelerate a charge

Q. A current I is passing through a wire having two sections P and Q of uniform diameters d and $\frac{d}{2}$ respectively. If the mean drift velocity of electrons in sections P and Q is denoted by $v_p$and $v_Q$respectively, then

1. $V_p=V_Q$
2. $V_p=\frac{1}{2}{V}_Q$
3. $V_p=\frac{1}{4}{V}_Q$
4. $V_p=2V_Q$

Q. A current I is passing through a wire having two sections P and Q of uniform diameters d and $\frac{d}{2}$ respectively. If the mean drift velocity of electrons in sections P and Q is denoted by $v_p$and $v_Q$respectively, then

1. $V_p=V_Q$
2. $V_p=\frac{1}{2}{V}_Q$
3. $V_p=\frac{1}{4}{V}_Q$
4. $V_p=2V_Q$

Q. A current flows in a wire of circular cross-section with the free electrons travelling with a mean drift velocity v. If an equal current flows in a wire of twice the radius, then the new mean drift velocity is

1. v
2. $\frac{v}{2}$
3. $\frac{v}{4}$
4. None of these

Q. When a current $I$ is set up in a wire of radius $r$, the drift velocity is $v_d$. If the same current is set up through a wire of radius $2r$ of same material, the drift velocity will be

1. $4v_d$
2. $\frac{v_d}{2}$
3. $2v_d$
4. $\frac{v_d}{4}$

Q. A steady current flows in a metallic conductor of non uniform cross-section. The quantity that remains constant along the length of the conductor is

1. current, electric field and drift speed
2. drift speed only
3. current and drift speed
4. current only

Q. When a current $I$ is set up in a wire of radius $r$, the drift velocity is $v_d$. If the same current is set up through a wire of radius $2r$ of same material, the drift velocity will be

1. $4v_d$
2. $\frac{v_d}{2}$
3. $2v_d$
4. $\frac{v_d}{4}$

Q. Even though the electron's drift speed and charge are so small, what is the main reason behind large amount of current in conductors?

1. Number of electrons is very high
2. Free electron's number density is enormous
3. Electrons are very light
4. Due to repulsion electrons travel at high speed