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5 months ago

Physics Class 11th

Does a higher amount of power always means efficient energy usage?

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Aadit Singh Uppal

Contributor-Level 10

No. Even if the power is higher, the energy can be inefficient. This happens when much of the energy generated gets wasted or isn't utilized as effectively as it should have been. In such cases, high power can still lead to inefficiency of energy.

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5 months ago

Physics Physics Moving Charges and Magnetism

Metallic disc of inner radius and outer radius $2 R$ is rotating with an angular speed w . What will be the electric potential difference that appears between the inner and outer periphery. The mass of electrons is $m$ and charge is $e$ .

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Vishal Baghel

Contributor-Level 10

Answer (1)

$e E = e \frac{d V}{d r} = m ω^{2} r$

$? V = \int d V = \int_{R}^{2 R} \frac{m}{e} ω^{2} r d r$

$= ? V = \frac{3 m ω^{2} R^{2}}{2 e}$

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5 months ago

Physics Class 12th

In the circuit shown below, maximum zener diode current will be _________mA.

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Payal Gupta

Contributor-Level 10

$l = \frac{120 - 60}{4000} = 0.015 A$

Thus l₂ = l - L_L

= 0.015 – 0.006

= 0.009 = 9mA

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5 months ago

Physics Physics Atoms

In the hydrogen spectrum, $λ$ be the wavelength of first transition line of Lyman series. The wavelength difference will be $" a λ "$ between the wavelength of 3^rd transition line of Paschen series and that 2^ndtransition line B Balmer series where a = __________.

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Payal Gupta

Contributor-Level 10

For first line of Lyman

$\frac{1}{λ} = R (1 - \frac{1}{4}) = R \frac{3}{4}$

$λ = \frac{4}{3 R}$

3rd line (Paschen)

$\frac{1}{λ_{3}} = R (\frac{1}{3^{2}} - \frac{1}{6^{2}}) = \frac{R}{9} * \frac{3}{4}$

2nd line (B almer)

${\frac{1}{λ}}_{2} = R (\frac{1}{2^{2}} - \frac{1}{4^{2}}) = \frac{R}{4} * \frac{3}{4}$

$a (\frac{4}{3 R}) = \frac{20}{3 R} \Rightarrow a = 5$

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5 months ago

Physics Physics Ray Optics and Optical Instruments

The graph between $\frac{1}{u} a n d \frac{1}{v}$ for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of lens is 1.5 and its both the surfaces have same radius of curvature R. The value of R will be _________cm. (where u = object distance, v = image distance)

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Payal Gupta

Contributor-Level 10

for point B, $\frac{1}{u} = - 0.10 c m^{- 1}, \frac{1}{v} = 0$

Thus u = 10 cm, v = $\infty$

i.e., f = 10 cm

$\frac{1}{10} = (1.5 - 1) (\frac{2}{R}) \Rightarrow \frac{1}{R} = \frac{1}{10}$

R = 10 cm

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5 months ago

Physics Physics Alternating Current

The effective current I in the given circuit at very high frequencies will be _________A.

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Payal Gupta

Contributor-Level 10

At very high frequencies

$X_{C} = \frac{1}{ω C} \to 0$

$X_{L} = ω L \to \infty$

Thus equivalent circuit

$Z = 1 + 2 + 2 = 5 Ω$

$l = \frac{220}{5} = 44 A$

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5 months ago

Physics Class 12th

Resistances are connected in a meter bridge circuit as shown in the figure. The balancing length $l_{2}$ is 40cm. Now as unknown resistance x is connected in series with P and new balancing length is found to be 80cm measured from the same end. Then the value of x will be _________ $Ω$ .

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Payal Gupta

Contributor-Level 10

Initially, $\frac{P}{Q} = \frac{40}{60} = \frac{2}{3}$ - (1)

Finally, $\frac{P + x}{Q} = \frac{80}{20} = \frac{4}{1}$

(2) (1)

$\frac{P + x}{P} = \frac{4 * 3}{2} = 6$

$\Rightarrow 1 + \frac{x}{P} = 6$

$\frac{x}{P} = 5$

x = 5 P = 5 * 4 = 20 $Ω$

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5 months ago

Physics Physics Electrostatic Potential and Capacitance

A composite parallel plate capacitor is made up to two different dielectric materials with different thickness (t₁ and t₂) as shown in figure. The two different dielectric materials are separated by a conducting foil F. The voltage of the conducing foil is ___________V.

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Payal Gupta

Contributor-Level 10

Capacitance of each capacitor

$C_{1} = \frac{A 3 ε_{0}}{\frac{1}{2}} = 6 A ε_{0}$

$C_{2} = A 4 ε_{0} = 4 A ε_{0}$

Equivalent capacitance

$Δ v_{2} = \frac{240 A ε_{0}}{4 A ε_{0}} = 60 v$

$v_{f o i l} = 60 v$

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5 months ago

Physics Physics Wave Optics

When a car is approaching the observer, the frequency of horn is 100Hz. After passing the observer, it is 50 Hz. If the observer moves with the car, the frequency will be $\frac{x}{3}$ Ha where x = _________.

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Payal Gupta

Contributor-Level 10

$f_{1} = 100 = f o (\frac{C}{C - V_{S}})$

C = Speed of sound

Vs = Speed of source

f2 = 50 = fo = $(\frac{C}{C + V_{s}})$

$\frac{f_{1}}{f_{2}} = 2 = \frac{C + V_{S}}{C - V_{S}}$

$f o = \frac{200}{3} = \frac{x}{3}$

x = 200

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5 months ago

Physics Units and Measurement

In an experiment to determine the Young's modulus of wire of a length exactly 1m, the extension in the length of the wire is measured as 0.4mm with an uncertainty of $\pm$ 0.02mm when a load of 1kg is applied. The diameter of the wire is measured as 0.4mm with an uncertainty of $\pm$ 0.02mm. The error in the measurement of Young's modulus $(Δ Y)$ is found to be x * 10¹⁰Nm^-2. The value of x is _________.

(take g = 10 ms^-2)

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Payal Gupta

Contributor-Level 10

L = 1 m

$Δ L = 0.4 * 1 0^{- 3} m$

$m = 1 k g$

d = 0.4 * 103 m

$\frac{F}{A} = y \frac{Δ L}{L}$

$y = \frac{F L}{A Δ L} = \frac{(m g) * 1}{(\frac{π d^{2}}{4}) * 0.4 * 1 0^{- 3}}$

$Δ y = 0.1 * 0.199 * 1 0^{12} = 1.99 * 1 0^{10}$

= 1.99

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