3.10 (a) In a meter bridge [Fig. 3.27], the balance point is found to be at 39.5 cm from the end A, when the resistor S is of 12.5 Ω. Determine the resistance of R. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?
(b) Determine the balance point of the bridge above if R and S are interchanged.
(c) What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current?
bridge is made of thick copper strips to minimize the resistance, which is not taken into consideration in the bridge formula.
(b) If R & S are interchanged, then and (100 - ) will also get interchanged. The balance point will be (100- from A. So the new balance point is 100 – 39.5 = 60.5 cm from A.
(c) When the galvanometer and cell are interchanged at the balance point of the bridge, the galvanometer will s
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3.10 (a) Balance point from end A, = 39.5 cm
Resistance of the resistor, S = 12.5 Ω
Condition for the balance is given as,
=
= 12.5 = 8.16 Ω
bridge is made of thick copper strips to minimize the resistance, which is not taken into consideration in the bridge formula.
(b) If R & S are interchanged, then and (100 - ) will also get interchanged. The balance point will be (100- from A. So the new balance point is 100 – 39.5 = 60.5 cm from A.
(c) When the galvanometer and cell are interchanged at the balance point of the bridge, the galvanometer will show no deflection, no current will flow through galvanometer.
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<p><strong>3.10 (a) </strong>Balance point from end A, <span title="Click to copy mathml"><math><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub></math></span> = 39.5 cm</p><p>Resistance of the resistor, S = 12.5 Ω</p><p>Condition for the balance is given as,</p><p><span title="Click to copy mathml"><math><mfrac><mrow><mrow><mi>R</mi></mrow></mrow><mrow><mrow><mi>S</mi></mrow></mrow></mfrac></math></span> = <span title="Click to copy mathml"><math><mfrac><mrow><mrow><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub><mi></mi></mrow></mrow><mrow><mrow><msub><mrow><mrow><mn>100</mn><mo>-</mo><mi></mi><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub></mrow></mrow></mfrac></math></span></p><p><span title="Click to copy mathml"><math><mi>R</mi><mo>=</mo><mi>S</mi><mo>×</mo><mfrac><mrow><mrow><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub><mi></mi></mrow></mrow><mrow><mrow><mn>100</mn><mo>-</mo><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub></mrow></mrow></mfrac></math></span> = 12.5 <span title="Click to copy mathml"><math><mo>×</mo><mfrac><mrow><mrow><mn>39.5</mn></mrow></mrow><mrow><mrow><mn>100</mn><mo>-</mo><mn>39.5</mn></mrow></mrow></mfrac></math></span> = 8.16 Ω</p><p><span title="Click to copy mathml"><math><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">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">c</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">b</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">w</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">n </mi><mi mathvariant="normal"></mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">r</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">i</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">a</mi><mi mathvariant="normal"></mi><mi mathvariant="normal">W</mi><mi mathvariant="normal">h</mi><mi mathvariant="normal">e</mi><mi mathvariant="normal">a</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">s</mi><mi mathvariant="normal">t</mi><mi mathvariant="normal">o</mi><mi mathvariant="normal">n</mi><mi mathvariant="normal">e</mi></math></span> bridge is made of thick copper strips to minimize the resistance, which is not taken into consideration in the bridge formula.</p><p><strong>(b)</strong> If R & S are interchanged, then <span title="Click to copy mathml"><math><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub></math></span> and (100 - <span title="Click to copy mathml"><math><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub></math></span> ) will also get interchanged. The balance point will be (100- <span title="Click to copy mathml"><math><msub><mrow><mrow><mi>l</mi></mrow></mrow><mrow><mrow><mn>1</mn></mrow></mrow></msub><mo>)</mo><mi></mi></math></span> from A. So the new balance point is 100 – 39.5 = 60.5 cm from A.</p><p><strong>(c)</strong> When the galvanometer and cell are interchanged at the balance point of the bridge, the galvanometer will show no deflection, no current will flow through galvanometer.</p>
According to this chapter, a galvanometer is used to find and measure the small electric currents in a circuit. The principle that works in a galvanometer is the electromagnetic induction.
There are two types of electricity - Static and Current electricity. The electric charges buildup on a material's surface is called the static electricity. The continuous flow of electric charge is termed as the current electricity. Current electricity is of two types - Alternating Current (AC) and Direct Current (DC). In AC, the charge direction reverses periodically and in DC, charge flows in one direction.
In simple words, current electricity can be defined as the electric charge continuously moving from one place to another along a pathway. It is measured in amperes (A). Electric current is needed for electrical devices to work.
No, in fact, it is one of the easiest chapter of class 12 Physics. Other chapters which are considered comparatively easy are Ray Optics and Electric Charges and Fields.
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