Two cells of same emf E but internal resistance r1 and r2 are connected in series to an external resistor R (figure). What should be the value of R so that the potential difference across the terminals of the first cell becomes zero?
This is a Short Answer Type Questions as classified in NCERT Exemplar
Explanation- according to ohms law
I=
The potential difference across terminal is
V=e-Ir= E- r1=0
E=
1=
R+r1+r2 = 2r1
R= r1-r2
<p>This is a Short Answer Type Questions as classified in NCERT Exemplar</p><p>Explanation- according to ohms law</p><p>I= <math><mfrac><mrow><mrow><mi>E</mi><mo>+</mo><mi>E</mi></mrow></mrow><mrow><mrow><mi>R</mi><mo>+</mo><mi>r</mi><mn>1</mn><mo>+</mo><mi>r</mi><mn>2</mn></mrow></mrow></mfrac></math></p><p>The potential difference across terminal is</p><p>V=e-Ir= E- <math><mfrac><mrow><mrow><mn>2</mn><mi>E</mi></mrow></mrow><mrow><mrow><mi>R</mi><mo>+</mo><mi>r</mi><mn>1</mn><mo>+</mo><mi>r</mi><mn>2</mn></mrow></mrow></mfrac></math> r1=0</p><p>E= <math><mfrac><mrow><mrow><mn>2</mn><mi>E</mi><mi>r</mi><mn>1</mn></mrow></mrow><mrow><mrow><mi>R</mi><mo>+</mo><mi>r</mi><mn>1</mn><mo>+</mo><mi>r</mi><mn>2</mn></mrow></mrow></mfrac></math></p><p>1= <math><mfrac><mrow><mrow><mn>2</mn><mi>r</mi><mn>1</mn></mrow></mrow><mrow><mrow><mi>R</mi><mo>+</mo><mi>r</mi><mn>1</mn><mo>+</mo><mi>r</mi><mn>2</mn></mrow></mrow></mfrac></math></p><p>R+r1+r2 = 2r1</p><p>R= r1-r2</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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