Ohm's Law in Scalar Form

Q. The charge on 500 cc of water due to protons will be

1. $6.0\times {10}^{27}C$
2. $2.67\times {10}^{7}C$
3. $6\times {10}^{23}C$
4. $1.67\times {10}^{23}C$

Q.

Two resistance wires on joining in parallel the resultant resistance is 6/5 ohms. One of the wire breaks the effective resistance is 2 ohms. The resistance of the broken wire is

Answer: 2 ohm

Q. A wire of resistance of 12 ohm per metre is bent to form a complete circle of radius 10cm .The resistance between its two diametrically opposite points A and B is?

Q. How to derive the Coulombs Law?

Q. Calculate the work done in moving a charge $-2\times {10}^{-9}C$ from A to B via C.

Q.

Obtain the equation $\overrightarrow{J}=\sigma \overrightarrow{E}$ of Ohms law on the basis of drift velocity.

Q. Electric flux through a surface of area $10m^2$ lying in the $xy$ plane is (if $\overrightarrow{E}=\hat{i}+\sqrt{2}\hat{j}+\sqrt{3}\hat{k}N/C$)

1. $141.4$
2. $200$
3. $100$
4. $17.32$

Q. A resistance of R $\Omega$ draws current from a potentiometer as shown in the figure. The potentiometer has a total resistance $R_0\Omega$. A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of the potentiometer.

Q. A potential difference of 10 V is applied across a conductor of 1000 Ω. The number of electrons flowing through the conductor in 300 s is (1) 1.875 × 1016 (2) 1.875 × 1017 (3) 1.875 × 1022 (4) 1.875 × 1019

Q. The ammeter shown in figure consists of a $480\Omega$ coil connected in parallel to a $20\Omega$ shunt. Find the reading of the ammeter.

1. $0.125A$
2. $0.225A$
3. $0.335A$
4. $0.445A$

Q. Time constant of given circuit in micro second is

Q. A conductor with rectangular cross section has dimensions $(a\times 2a\times 4a)$ as shown in figure. Resistance across AB is 'x', across CD is 'y' and across EF is 'z'. Then

1. x = y = z
2. x > y > z
3. y > z > x
4. x > z > y

Q. The earth’s surface has a negative surface charge density of 10–9 Cm–2. The potential difference of 400 kV between the top of theatmosphere and the surface results (due to the low conductivity ofthe lower atmosphere) in a current of only 1800 A over the entireglobe. If there were no mechanism of sustaining atmospheric electric field, how much time (roughly) would be required to neutralise theearth’s surface? (This never happens in practice because there is amechanism to replenish electric charges, namely the continualthunderstorms and lightning in different parts of the globe). (Radiusof earth = 6.37 × 106 m.)

Q.

n identical cells are joined in series with its two cells A and B in the loop with reversed polarities. Emf of each cell is E and internal resistance r. The potential difference across cell A or B is (Here n > 4)

1. $2E(1-\frac{1}{n})$

2. $\frac{2E}{n}$

3. $\frac{4E}{n}$

4. $2E(1-\frac{2}{n})$

Q. Consider the circuit shown. If all the cells have negligible internal resistance, what will be the current through the $2\Omega$ resistor when steady state is reached ?

1. 0.29 A
2. 0 A
3. 0.66 A
4. 0.14 A

Q. Two wires of the same material having lengths in the ratio 2:3, are connected in series. The potential differences across the wires are 4.2V and 3.6V respectively. The ratio of their radii would be:

1. $2:\sqrt{7}$
2. $2:7$
3. $\sqrt{7}:2$
4. $7:2$

Q. three unequal resistors in parallel are equivalent to resistence 1ohm .if 2 of them are in ratio 1:2 and ifno resis†an ce value is fractonal, the largest of three resisances in ohm is (1) 4 (2) 6 (3) 5 (4)1

Q.

A wire of resistance x ohm is drawn out, so that its length is increased to twice its original length, and its new resistance becomes 20 Ω then x will be

Q.

What happens to resistance when the length is doubled without steching it?

Q.

If $500J$ of work is required to carry a $40C$charge slowly from one to point another in an electric field, then the potential difference between these two points is

1. $12.5V$

2. $20kV$

3. $0.08V$

4. Depends upon the path

Q.

The current through an inductor of $1H$ is given by $i=3t\sin \left(t\right)$. The voltage across the inductor of $1H$ is

1. $3\left(\sin t+3\cos t\right)$

2. $3\left(\sin t+t.\cos t\right)$

3. $4\left(\sin t+5\cos t\right)$

4. $8\left(3\sin t+5\cos t\right)$

Q.

Two unknown resistances X and Y are connected in left and right gaps of a metre bridge and the balancing point is obtained at 50 cm from left. When a $20\Omega$ resistance is connected in series with X, the balancing point is at 60 cm from left. The values of X and Y respectively (in ohms) are

1. 40, 10

2. 40, 20

3. 20, 20

4. 40, 40

Q. The specific resistance P of a circular wire of radius r, resistance R, and length / is given by P = πr²R/t (given r = 0.24 + 0.02cm, R = 30 + 1 n, and / = 4.80 + 0.01 cm.) The percentage error in P is nearly??

Q.

Calculate the amount of charge flowing in $2\min$ in a wire of resistance $10\mathrm{\Omega }$ when a potential difference of $20\mathrm{V}$ is applied between its ends?

Q.

What is Ohms Law? What are its limitaions?

Q. Two resistance r1 and r2 (r1< r2) are joined in parallel. The equivalent resistance R is such that 1 R > r1 + r2 2 R > √r1 +√r2 3 r1 < R < r2 4 R < r1

Q. Shown in the figure below is a meter-bridge set up with null deflection in the galvanometer. The value of the unknown resistor $R$ is

1. $220\Omega$
2. $110\Omega$
3. $55\Omega$
4. $13.75\Omega$

Q.

A voltmeter has a resistance of $2000\mathrm{ohms}$ and it can measure up to $2\mathrm{V}$. If we want to increase its range to $10\mathrm{V}$, then the required resistance in series will be?

1. 8000 Omega

2. 4000 Omega

3. 6000 Omega

4. 2000 Omega

Q. The equivalent inductance of two inductances is 2.4 henry when connected in parallel and 10 henry when connected in series. The difference betweenthe two inductances is (1) 2 henry (2) 3 henry (3) 4 henry(4) 5 henry

Q. A battery of internal resistance $r$ having no load resistance has an e.m.f. $E$ volt. What is the observed e.m.f across the terminals of the battery when a load resistance $R(=r)$ is connected to its terminals?

1. $2Evolt$
2. $Evolt$
3. $\frac{E}{2}volt$
4. $\frac{E}{4}volt$