$\frac{k q_1 q_2}{r^2}$
D. $F=\frac{4_1 4_2}{4 \pi \varepsilon_0 r^2}$

10. The Imaginary surface necessary to apply Gass Law is called

Bipolar Surface
Q. Gaussian Surface
1. None of the above
A. Cartestan Surface.

11. If the surface under consideration is not perpendicular to the field lines then the expect son to given as A. $\Sigma E A \cos \theta$
b. $\sum E A \cos \pi$
C. $\Sigma E \cos \theta$
D. $\sum A \cos \theta$

12. What is the integral form of the expression $\sum F A \cos \theta=\frac{q}{\varepsilon_0}$?
A. $\int E \cdot d A=\frac{?}{\varepsilon_0}$
B $\int E+A=\frac{q}{\varepsilon_0}$
C. $\int A$.
D. $\int B / A=\frac{9}{\varepsilon_0}$

13. The expression for current density flowing through a conductor is represented by
A. qnAl
B. qnAd
C. qnAVd
D. qnVd

14. A 10 m length of copper wire has a diameter of 1.5 mm . Find the current density if it carries 1.2A.
A. $6.7897 \times 10^6 A / m ^2$
B. $6.7897 \times 10^5 A / m ^2$
C. $6.7897 \times 10^4 Alm ^2$
D. 6789

15. Which of the following expressions is not a representation of Ohm's law?
x. $\frac{\pi}{\sigma A}$
B. $\frac{11 . \rho}{A}$
C. jpl
D. pE

16. The null deflection of a Potentiometer refers to
A. When the galvanometer attached to the jockoy deflects to the left
B. When the galvanometer attached to the jockey deflects to the right
C. When the galvanometer attached to the jockey rotates through 180 degrees

The imaginary surface in Gauss's Law is the Gaussian Surface.
Electric flux when the surface is not perpendicular to the field lines is ∑ E A cos θ .
The integral form of Gauss's Law is ∫ E ⋅ d A = ε 0 ​ q ​ .
Current density is given by q n A v d ​ .
The calculated current density for the wire is approximately 6.79 × 1 0 5 A / m 2 .
The expression that is NOT a representation of Ohm's Law is σ A π ​ .
Null deflection in a potentiometer indicates a balanced state. See individual answers above. ​

Explanation

Introduction We will address each multiple-choice question sequentially, providing the correct answer and a brief explanation.

Question 10 - Gauss's Law Question 10: The imaginary surface necessary to apply Gauss's Law is called a Gaussian Surface. So the answer is Q.

Question 11 - Electric Flux Question 11: If the surface under consideration is not perpendicular to the field lines, the expression is given as ∑ E A cos θ . So the answer is A.

Question 12 - Integral Form of Gauss's Law Question 12: The integral form of Gauss's Law is ∫ E ⋅ d A = ε 0 ​ q ​ . So the answer is A.

Question 13 - Current Density Question 13: The expression for current density flowing through a conductor is represented by q n A v d ​ . So the answer is C.

Question 14 - Calculating Current Density Question 14: Given a copper wire with length 10 m, diameter 1.5 mm, and current 1.2 A, we need to find the current density. The formula for current density is J = A I ​ , where I is the current and A is the cross-sectional area. The radius r is half the diameter, so r = 2 1.5 × 1 0 − 3 ​ = 0.75 × 1 0 − 3 m. The area A = π r 2 = π ( 0.75 × 1 0 − 3 ) 2 ≈ 1.767 × 1 0 − 6 m 2 . Therefore, the current density J = 1.767 × 1 0 − 6 1.2 ​ ≈ 6.79 × 1 0 5 A / m 2 . So the answer is B.

Question 15 - Ohm's Law Question 15: We need to identify which expression is NOT a representation of Ohm's Law. Ohm's Law can be expressed as J = σ E , where J is current density, σ is conductivity, and E is the electric field. Also, V = I R , where V is voltage, I is current, and R is resistance. Resistance can be written as R = A ρl ​ , where ρ is resistivity, l is length, and A is area. σ A π ​ does not directly represent Ohm's law. The other options can be derived from Ohm's law. So the answer is x.

Question 16 - Potentiometer Question 16: The null deflection of a Potentiometer refers to when the galvanometer attached to the jockey shows no current flow, indicating a balanced state. This typically happens when the galvanometer attached to the jockey deflects to zero. None of the provided options perfectly describe this, but we can assume it refers to a balanced state.

Final Answers Final Answers:

Q. Gaussian Surface

A. ∑ E A cos θ

A. ∫ E ⋅ d A = ε 0 ​ q ​

C. qnAVd

B. 6.7897 × 1 0 5 A / m 2

x. σ A π ​

The question is incomplete, but the closest answer would relate to a balanced state with null deflection.


Examples
These physics concepts are fundamental in electrical engineering and electromagnetism. For example, understanding Gauss's Law is crucial in designing capacitors and analyzing electric fields. Calculating current density is essential in determining the appropriate wire size for electrical circuits to prevent overheating. Ohm's Law is the backbone of circuit analysis, allowing engineers to predict voltage, current, and resistance in various components. These principles are applied daily in designing and maintaining electrical systems, from household appliances to complex industrial machinery.

Answered by GinnyAnswer | 2025-07-08

The Gaussian Surface is crucial for Gauss's Law, while the expression for electric flux not perpendicular to the field lines is Σ E A cos θ . Current density is represented by q n A v d ​ , the calculated current density in a copper wire is approximately 6.79 × 1 0 5 A / m 2 , and the expression not representing Ohm's law is σ A π ​ .

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Answered by Anonymous | 2025-08-17