Tag: current electricity

Questions Related to current electricity

Two equal resistances are connected in the gaps of a meter bridge. If the resistance in the left gap is increased by $10\%$, the balancing point shift :

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. $10\%$ to right

  2. $10\%$ to left

  3. $9.6\%$ to right

  4. $4.8\%$ to right

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Correct Option: D
Explanation:
Let the Resistance be R,

Initially
$\dfrac{R}{R}  = \dfrac{l}{100-l}$
     $ \Rightarrow  l = 50 cm$
After 10% increase it is,

$ \Rightarrow  \dfrac{1.1R}{R} = \dfrac{l}{100-l}$

$ \Rightarrow  110  = 2.1 l$

$ \Rightarrow  l = \dfrac{110}{2.1} = 52.38$

$ \Rightarrow  \dfrac{\Delta l}{l} \times 100 = \dfrac{2.38}{50}\times 100  \approx 4.8$%

The balancing point in a meter bridge is 44 cm. If the resistances in the are  gaps are  inchanged   the new balance point is 

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. 44 cm

  2. 56 cm

  3. 50 cm

  4. 22 cm

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Correct Option: B
Explanation:

At balance position of meter bridge $=\dfrac{I}{{\left( {100 - I} \right)}}$ $=\frac{R}{S}$

Where $I$ is the balancing length$.$
So$,$ if value of $R$ and $S$ are inter changed the new $I$ limit will be $100-44=56$
Hence,
option $(B)$ is correct answer.

In a meter bridge setup, which of the following should be the properties of the one meter long wire?

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. High resistivity and low temperature coefficient

  2. Low resistivity and low temperature coefficient

  3. Low resistivity and high temperature coefficient

  4. High resistivity and high temperature coefficient

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Correct Option: A

A $6\Omega$ resistance is connected in the left gap of a meter bridge. In the second gap $3\Omega$ and $6\Omega$ are joined in parallel. The balance point of the bridge is at __

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. $75cm$

  2. $60cm$

  3. $30cm$

  4. $25cm$

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Correct Option: D

With a potentiometer null points were obtained at $140cm$ and $180cm$ for cells of emf $1.1V$ and one unknown $X$ volt. UNknown emf is: 

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. $1.1V$

  2. $1.8V$

  3. $2.4V$

  4. $1.41V$

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Correct Option: D

The length of a potentiometer wire is $l$ A cell of emf E is balanced at a length $\dfrac{l }{ 3}$ from the positive end of the wire. If the length of the wire is increased by $\dfrac{l} { 2}$.
At what distance will the same cell give a balance point?

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. $

    \dfrac{2l}{3}

    $

  2. $

    \dfrac{l}{2}

    $

  3. $

    \dfrac{l}{6}

    $

  4. $

    \dfrac{4l}{3}

    $

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Correct Option: B

In Wheatstone's bridge $  P=9  $ ohm, $  Q=11  $ ohm, $  R=4  $ ohm and $  S=6  $ ohm. How much resistance must be put in parallel to the resistance $  S  $ to balance the bridge

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. $24 ohm$

  2. $ \frac{44}{9} ohm$

  3. $26.4 \mathrm{ohm} $

  4. $18.7 ohm$

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Correct Option: C

In metre bridge experiment, with a standard resistance in the right gap and a resistance coil dipped in water (in a beaker) in the left gap, the balancing length obtained is 'l'. If the temperature of water is increased, the new balancing length is

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. >l

  2. none

  3. =0

  4. =l

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Correct Option: A
Explanation:

$\begin{array}{l} \frac { { { R _{ unknown } } } }{ { { R _{ s\tan  dard } } } } =\frac { l }{ { \left( { 1-l } \right)  } } . \ If\, \, temperature\, \, increases,\, \, resis\tan  ce\, \, increases. \end{array}$

Hence, Option $A$ is correct.

An electron is released from the origin at a place where a uniform electric field $\overrightarrow{E}$ and uniform magnetic field $\overrightarrow{B}$ exit along the negative y-axis and the negative z-axis respectively.

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. At time $t$ the y-component of velocity of the electron becomes $u _y = \dfrac{E}{B}\sin \omega t$ where $\omega = \dfrac{eB}{m}$.

  2. At $t = \pi m / eB$ the electron will have only x-component of velocity.

  3. At $t = \dfrac{2\pi m}{3eB}$, the y-component of velocity becomes zero.

  4. The displacement along y-axis is $\dfrac{2Em}{eB^2}$ when the velocity of electron becomes perpendicular to the y-axis

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Correct Option: A,B

Two wires of resistances X and Y are connected in left and a right gap respectively of a slide wire bridge of length 170cm. The null point is obtained at the center of the wire. Now, the wire X is given a shape of a ring and two diametrically opposite points are connected in the left gap. The wire Y is stretched to double of its original length and is connected in the right gap. Find the shift in the null point:

physics current electricity meter bridge meter bridge and problems on it galvanometer

  1. 75 cm

  2. 10 cm

  3. 126 cm

  4. Zero

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Correct Option: A