Overview

The circuit shown in the figure is in steady state for a long time. The connection to battery is suddenly broken (switch S is opened up). What is the charge (in $μ C$ ) on the capacitor after 0.001 sec.?

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Contributor-Level 10

$i_{i} = \frac{84}{140} = 0.6 A$

$i_{2} = \frac{84}{60} = 1.4 A$

p.d across capacitor = 20 v

Q = CV = 5 * 20 = 100 $? C$

After S is open

Q = Q . e^-t/RC

=100 e^-4

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5 months ago

In the figure shown below, the maximum and minimum possible unknown resistance (X), that can be measured by the post office box are X_max and X_minrespectively. Then the ratio of these two resistances is: (In this experiment, we take out only one plug in arm AB and only one plug in arm BC, but in arm AD we can take any no. of plugs):

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Contributor-Level 10

$\frac{P}{Q} = \frac{R}{X} X_{m a x} = \frac{R_{m a x} . Q_{m a x}}{P_{m i n}}$

$= 9000 * \frac{1000}{10} = 9 * 1 0^{5} o h m$

$x_{m i n} = \frac{R_{m i n} . Q_{m i n}}{P_{m a x}} = 100 * \frac{10}{1000} = 1 o h m$

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5 months ago

In the colour coding system of carbon resistors, the tolerance (in %) shown by gold band is ____.

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Contributor-Level 10

Gold band is equal to 5% tolerance

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5 months ago

A composite rod made up of two conductors of resistivity ρ₁ and ρ₂ is show in the figure. If face A and B are connected to a battery, find the resistance of the rod.

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Contributor-Level 10

R? = (ρ? L)/a² R? = (ρ? L)/ (3a²)
Both are in parallel . R? = (R? )/ (R? +R? ) = (ρ? ρ? L)/ (a² (3ρ? +ρ? )

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5 months ago

A resistor develops 300 J of thermal energy in 15s, when a current of 2 A is passed through it. If the current increases to 3 A, the energy developed in 10s is…………….J.

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Raj Pandey

Contributor-Level 9

$H = I^{2} R t = 2^{2} * R * 15$

$\Rightarrow 300 = 60 R$

$R = 5 Ω$

Now for 3A, time = 10 sec

$H' = l^{2} R t = 3^{2} * 5 * 10 = 450 J$

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5 months ago

A current through a wire-depends on time as

i = a₀t + bt²

Where a₀ = 20A/s and b = 8As^-². Find the charge crossed through a section of the wire in 15s.

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Contributor-Level 10

$\frac{d q}{d t} = t = 20 t + 8 t^{2}$

$\Rightarrow \int_{0}^{q} d q = \int_{0}^{15} (20 t + 8 t^{2}) d t$

$\Rightarrow q = 20 * \frac{1 5^{2}}{2} + 8 . \frac{1 5^{3}}{3} = 11250 C$

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5 months ago

A cell E₁ of emf 6V and internal resistance $2 Ω$ is connected with another cell E₂ of emf 4V and internal resistance $8 Ω$ (as shown in the figure). The potential difference across points X and Y is:

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Contributor-Level 10

$i = \frac{6 - 4}{2 + 8} = 0.2 A$

$V_{x} + 4 + 0.2 * 8 = V_{Y}$

$\Rightarrow V_{Y} - V_{X} = 5.6 V$

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5 months ago

A teacher in his physics laboratory allotted an experiment ot determine the resistance (G) of a galvanometer. Students took the observations for $\frac{1}{3}$ $\frac{}{}$ deflection in the galvanometer. Which of the below is true for measuring value of G?

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Raj Pandey

Contributor-Level 9

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New answer posted

5 months ago

In the colour coding system of carbon resistors, the tolerance (in %) shown by gold band is ______.

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Contributor-Level 10

Gold band is equal to 5% tolerance

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New answer posted

5 months ago

A multi range current ammeter can be constructed by using a galvanometer circuit as shown in figure. We want a current meter that can measure 10 mA, 100 mA and 1A using a galvanometer of resistance 10 Ω and that produces maximum deflection for current 1 mA. Value of S₁ + S₂ + S₃ in ohms is

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