00. Electric Current, Current Density and Drift Velocity
Current Electricity

151766 When a current $I$ flows through a wire, the drift velocity of the electrons is $v$. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

1 $\frac{\mathrm{v}}{8}$
2 $\frac{\mathrm{v}}{4}$
3 $\frac{\mathrm{v}}{2}$
4 $\mathrm{v}$
5 $2 \mathrm{v}$
Current Electricity

151767 The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

1 $6: 5$
2 $5: 6$
3 $\text { } 3: 2
4 \text { } 2: 3$
Current Electricity

151768 How many electrons per second constitute a current of one microampere?

1 One electron
2 $10^{-6}$ electrons
3 $10^{6}$ electrons
4 $6.25 \times 10^{12}$ electrons
Current Electricity

151771 In hydrogen discharge tube, it is observed that through a given cross-section $3.13 \times 10^{15}$ electrons are moving from right to left and $3.12 \times 10^{15}$ protons are moving from left to right. The current in the discharge tube and its direction will be

1 $2 \mathrm{~mA}$ towards left
2 $2 \mathrm{~mA}$, towards right
3 $1 \mathrm{~mA}$, towards right
4 $2 \mathrm{~mA}$, towards left
Current Electricity

151772 Charge passing through a conductor of cross section area $A=0.3 \mathrm{~m}^{2}$ is given by $q=3 t^{2}+5 t+$ 2 in coulomb, where $t$ is in second. What is the value of drift velocity at $t=2 s$ ?
(Given, $\mathbf{n}=\mathbf{2} \times 10^{25} / \mathrm{m}^{3}$ )

1 $0.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
2 $1.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
3 $2.08 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
4 $0.57 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
Current Electricity

151766 When a current $I$ flows through a wire, the drift velocity of the electrons is $v$. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

1 $\frac{\mathrm{v}}{8}$
2 $\frac{\mathrm{v}}{4}$
3 $\frac{\mathrm{v}}{2}$
4 $\mathrm{v}$
5 $2 \mathrm{v}$
Current Electricity

151767 The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

1 $6: 5$
2 $5: 6$
3 $\text { } 3: 2
4 \text { } 2: 3$
Current Electricity

151768 How many electrons per second constitute a current of one microampere?

1 One electron
2 $10^{-6}$ electrons
3 $10^{6}$ electrons
4 $6.25 \times 10^{12}$ electrons
Current Electricity

151771 In hydrogen discharge tube, it is observed that through a given cross-section $3.13 \times 10^{15}$ electrons are moving from right to left and $3.12 \times 10^{15}$ protons are moving from left to right. The current in the discharge tube and its direction will be

1 $2 \mathrm{~mA}$ towards left
2 $2 \mathrm{~mA}$, towards right
3 $1 \mathrm{~mA}$, towards right
4 $2 \mathrm{~mA}$, towards left
Current Electricity

151772 Charge passing through a conductor of cross section area $A=0.3 \mathrm{~m}^{2}$ is given by $q=3 t^{2}+5 t+$ 2 in coulomb, where $t$ is in second. What is the value of drift velocity at $t=2 s$ ?
(Given, $\mathbf{n}=\mathbf{2} \times 10^{25} / \mathrm{m}^{3}$ )

1 $0.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
2 $1.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
3 $2.08 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
4 $0.57 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
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Current Electricity

151766 When a current $I$ flows through a wire, the drift velocity of the electrons is $v$. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

1 $\frac{\mathrm{v}}{8}$
2 $\frac{\mathrm{v}}{4}$
3 $\frac{\mathrm{v}}{2}$
4 $\mathrm{v}$
5 $2 \mathrm{v}$
Current Electricity

151767 The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

1 $6: 5$
2 $5: 6$
3 $\text { } 3: 2
4 \text { } 2: 3$
Current Electricity

151768 How many electrons per second constitute a current of one microampere?

1 One electron
2 $10^{-6}$ electrons
3 $10^{6}$ electrons
4 $6.25 \times 10^{12}$ electrons
Current Electricity

151771 In hydrogen discharge tube, it is observed that through a given cross-section $3.13 \times 10^{15}$ electrons are moving from right to left and $3.12 \times 10^{15}$ protons are moving from left to right. The current in the discharge tube and its direction will be

1 $2 \mathrm{~mA}$ towards left
2 $2 \mathrm{~mA}$, towards right
3 $1 \mathrm{~mA}$, towards right
4 $2 \mathrm{~mA}$, towards left
Current Electricity

151772 Charge passing through a conductor of cross section area $A=0.3 \mathrm{~m}^{2}$ is given by $q=3 t^{2}+5 t+$ 2 in coulomb, where $t$ is in second. What is the value of drift velocity at $t=2 s$ ?
(Given, $\mathbf{n}=\mathbf{2} \times 10^{25} / \mathrm{m}^{3}$ )

1 $0.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
2 $1.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
3 $2.08 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
4 $0.57 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
Current Electricity

151766 When a current $I$ flows through a wire, the drift velocity of the electrons is $v$. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

1 $\frac{\mathrm{v}}{8}$
2 $\frac{\mathrm{v}}{4}$
3 $\frac{\mathrm{v}}{2}$
4 $\mathrm{v}$
5 $2 \mathrm{v}$
Current Electricity

151767 The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

1 $6: 5$
2 $5: 6$
3 $\text { } 3: 2
4 \text { } 2: 3$
Current Electricity

151768 How many electrons per second constitute a current of one microampere?

1 One electron
2 $10^{-6}$ electrons
3 $10^{6}$ electrons
4 $6.25 \times 10^{12}$ electrons
Current Electricity

151771 In hydrogen discharge tube, it is observed that through a given cross-section $3.13 \times 10^{15}$ electrons are moving from right to left and $3.12 \times 10^{15}$ protons are moving from left to right. The current in the discharge tube and its direction will be

1 $2 \mathrm{~mA}$ towards left
2 $2 \mathrm{~mA}$, towards right
3 $1 \mathrm{~mA}$, towards right
4 $2 \mathrm{~mA}$, towards left
Current Electricity

151772 Charge passing through a conductor of cross section area $A=0.3 \mathrm{~m}^{2}$ is given by $q=3 t^{2}+5 t+$ 2 in coulomb, where $t$ is in second. What is the value of drift velocity at $t=2 s$ ?
(Given, $\mathbf{n}=\mathbf{2} \times 10^{25} / \mathrm{m}^{3}$ )

1 $0.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
2 $1.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
3 $2.08 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
4 $0.57 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
Current Electricity

151766 When a current $I$ flows through a wire, the drift velocity of the electrons is $v$. When current 2I flows through another wire of the same material having double the length and double the area of cross-section, the drift velocity of the electrons will be

1 $\frac{\mathrm{v}}{8}$
2 $\frac{\mathrm{v}}{4}$
3 $\frac{\mathrm{v}}{2}$
4 $\mathrm{v}$
5 $2 \mathrm{v}$
Current Electricity

151767 The contribution in the total current flowing through a semiconductor due to electrons and holes are $\frac{3}{4}$ and $\frac{1}{4}$ respectively. If the drift velocity of electrons is $\frac{5}{2}$ times that of holes at this temperature, then the ratio of concentration of electrons and holes is

1 $6: 5$
2 $5: 6$
3 $\text { } 3: 2
4 \text { } 2: 3$
Current Electricity

151768 How many electrons per second constitute a current of one microampere?

1 One electron
2 $10^{-6}$ electrons
3 $10^{6}$ electrons
4 $6.25 \times 10^{12}$ electrons
Current Electricity

151771 In hydrogen discharge tube, it is observed that through a given cross-section $3.13 \times 10^{15}$ electrons are moving from right to left and $3.12 \times 10^{15}$ protons are moving from left to right. The current in the discharge tube and its direction will be

1 $2 \mathrm{~mA}$ towards left
2 $2 \mathrm{~mA}$, towards right
3 $1 \mathrm{~mA}$, towards right
4 $2 \mathrm{~mA}$, towards left
Current Electricity

151772 Charge passing through a conductor of cross section area $A=0.3 \mathrm{~m}^{2}$ is given by $q=3 t^{2}+5 t+$ 2 in coulomb, where $t$ is in second. What is the value of drift velocity at $t=2 s$ ?
(Given, $\mathbf{n}=\mathbf{2} \times 10^{25} / \mathrm{m}^{3}$ )

1 $0.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
2 $1.77 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
3 $2.08 \times 10^{-5} \mathrm{~m} / \mathrm{s}$
4 $0.57 \times 10^{-5} \mathrm{~m} / \mathrm{s}$