1.18 A point charge +10 μC is a distance 5 cm directly above the centre of a square of side 10 cm, as shown in Fig. 1.34. What is the magnitude of the electric flux through the square? (Hint: Think of the square as one face of a cube with edge 10 cm.)
1.18 The square can be considered as one face of a cube of edge 10 cm with a centre where charge q is placed.
According to Gauss’s theorem for a cube, total electric flux is through all its six faces.
i.e. through the square is = ,Where= Permittivity of free space = 8.854
We have q = +10
Hence, = = == 188238.83 N = 1.88 N
<p><strong>1.18 </strong>The square can be considered as one face of a cube of edge 10 cm with a centre where charge q is placed.</p><p>According to Gauss’s theorem for a cube, total electric flux is through all its six faces.</p><p> <span title="Click to copy mathml"><math><msub><mrow><mrow><mi>φ</mi></mrow></mrow><mrow><mrow><mi>T</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>l =</mi></mrow></mrow></msub></math></span><span title="Click to copy mathml"><math><mfrac><mrow><mrow><mi>q</mi></mrow></mrow><mrow><mrow><msub><mrow><mrow><mi>?</mi></mrow></mrow><mrow><mrow><mn>0</mn></mrow></mrow></msub></mrow></mrow></mfrac></math></span> </p><p><span title="Click to copy mathml"><math><mi mathvariant="normal">H</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">e</mi><mo>,</mo><mi mathvariant="normal"></mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">l</mi><mi mathvariant="normal">u</mi><mi mathvariant="normal">x</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">h</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">u</mi><mi mathvariant="normal">g</mi><mi mathvariant="normal">h</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">f</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">f</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">h</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">u</mi><mi mathvariant="normal">b</mi><mi mathvariant="normal">e</mi></math></span> i.e. through the square is <span title="Click to copy mathml"><math><mi>φ</mi><mo>=</mo><mi></mi><mfrac><mrow><mrow><msub><mrow><mrow><mi>φ</mi></mrow></mrow><mrow><mrow><mi>T</mi><mi>o</mi><mi>t</mi><mi>a</mi><mi>l</mi></mrow></mrow></msub></mrow></mrow><mrow><mrow><mn>6</mn></mrow></mrow></mfrac></math></span> = <span title="Click to copy mathml"><math><mfrac><mrow><mrow><mi>q</mi></mrow></mrow><mrow><mrow><msub><mrow><mrow><mn>6</mn><mi>?</mi></mrow></mrow><mrow><mrow><mn>0</mn></mrow></mrow></msub></mrow></mrow></mfrac><mi></mi></math></span> ,Where<span title="Click to copy mathml"><math><msub><mrow><mrow><mi>?</mi></mrow></mrow><mrow><mrow><mn>0</mn></mrow></mrow></msub></math></span>= Permittivity of free space = 8.854 <span title="Click to copy mathml"><br></span> <span title="Click to copy mathml"><math><mo>×</mo><msup><mrow><mrow><mn>10</mn></mrow></mrow><mrow><mrow><mo>-</mo><mn>12</mn></mrow></mrow></msup></math></span> <span title="Click to copy mathml"><math><msup><mrow><mrow><mi>C</mi></mrow></mrow><mrow><mrow><mn>2</mn></mrow></mrow></msup><msup><mrow><mrow><mi>N</mi></mrow></mrow><mrow><mrow><mo>-</mo><mn>1</mn></mrow></mrow></msup></math></span><span title="Click to copy mathml"><math><msup><mrow><mrow><mi>m</mi></mrow></mrow><mrow><mrow><mo>-</mo><mn>2</mn></mrow></mrow></msup></math></span></p><p>We have q = +10 <span title="Click to copy mathml"><math><mi>μ</mi><mi></mi><mi>C</mi></math></span></p><p>Hence, = <span title="Click to copy mathml"><math><mi>φ</mi></math></span> = <span title="Click to copy mathml"><math><mfrac><mrow><mrow><mi>q</mi></mrow></mrow><mrow><mrow><msub><mrow><mrow><mn>6</mn><mi>?</mi></mrow></mrow><mrow><mrow><mn>0</mn></mrow></mrow></msub></mrow></mrow></mfrac></math></span> =<span title="Click to copy mathml"><math><mfrac><mrow><mrow><mn>10</mn><mo>×</mo><msup><mrow><mrow><mn>10</mn></mrow></mrow><mrow><mrow><mo>-</mo><mn>6</mn></mrow></mrow></msup></mrow></mrow><mrow><mrow><mn>6</mn><mo>×</mo><mn>8.854</mn><mi mathvariant="normal"></mi><mo>×</mo><msup><mrow><mrow><mn>10</mn></mrow></mrow><mrow><mrow><mo>-</mo><mn>12</mn></mrow></mrow></msup></mrow></mrow></mfrac></math></span>= 188238.83 N<span title="Click to copy mathml"><math><msup><mrow><mrow><mi>m</mi></mrow></mrow><mrow><mrow><mn>2</mn></mrow></mrow></msup><msup><mrow><mrow><mi>C</mi></mrow></mrow><mrow><mrow><mo>-</mo><mn>1</mn></mrow></mrow></msup></math></span> = 1.88<span title="Click to copy mathml"><math><mo>×</mo><msup><mrow><mrow><mn>10</mn></mrow></mrow><mrow><mrow><mn>5</mn></mrow></mrow></msup></math></span> N<span title="Click to copy mathml"><math><msup><mrow><mrow><mi>m</mi></mrow></mrow><mrow><mrow><mn>2</mn></mrow></mrow></msup><msup><mrow><mrow><mi>C</mi></mrow></mrow><mrow><mrow><mo>-</mo><mn>1</mn></mrow></mrow></msup></math></span> </p>
The following are the topics covered in this chapter: Electric Field and Field Lines, Gauss's Law, Electric Dipole, Conductors and Insulators, and Electric Flux.
Indeed, it is an easy chapter of Class 12 Physics. In this chapter, you will learn about the foundational concepts like Gauss's law and electric fields.
In the medical entrance test NEET, this chapter has a moderate weightage. You can expect around 2-3 questions of this chapter that contributes to the 3-5% of the total marks in the Physics section.
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