Physics

Contributor-Level 10

In an LCR series AC circuit, the phase difference φ between current and voltage is: φ = tan? ¹ (X? - X? ) / R)

If each vibrational mode contributes two degrees of freedom and the total degrees of freedom f = 3 + 3 + 4 = 10, then:
β = 1 + 2/f = 1 + 2/10 = 1.2

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7 months ago

A radioactive sample disintegrates via two independent decay processes having half lives T?/?¹? and T?/?²? respectively. The effective half-life, T?/? of the nuclei is:

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Physics Physics Electromagnetic Waves

Contributor-Level 9

From Radioactive Decay Law,
dN/dt = λ? N + λ? N = λ_eff N
⇒ λ_eff = λ? + λ? ⇒ ln (2)/T = ln (2)/T? + ln (2)/T? ⇒ T = (T? ) / (T? + T? )
(where T, T? , and T? are half-lives)

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7 months ago

A plane electromagnetic wave of frequency 100 MHz is traveling in vacuum along the x-direction. At a particular point in space and time, B = 2.0 * 10? k? T. (where, k? is unit vector along z-direction) What is E at this point? (speed of light c = 3 x 10? m/s)

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Contributor-Level 9

Direction of E is perpendicular to the direction of propagation and that of B.
E = cB = 3 * 10? * 2 * 10? = 6 V/m

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7 months ago

Match List-I with List-II

List - I	List - II
(a) Phase difference between current and voltage in a purely resistive AC circuit	(i) π/2; current leads voltage
(b) Phase difference between current and voltage in a pure inductive AC circuit	(ii) Zero
(c) Phase difference between current and voltage in a pure capacitive AC circuit	(iii) π/2; current lags voltage
(d) Phase difference between current and voltage in an LCR series circuit	(iv) tan?¹((X_L - X_C)/R)

Choose the most appropriate answer from the options given below :

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Physics Physics Magnetism and Matter

Contributor-Level 10

In a purely resistive AC circuit, if V = V? sin (ωt), then the current I is:
I = (V? / X? ) * sin (ωt - π/2)

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7 months ago

Four identical long solenoids A, B, C and D are connected to each other as shown in the figure. If the magnetic field at the centre of A is 3T, the field at the centre of C would be: (Assume that the magnetic field is confined within the volume of respective solenoid).

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Contributor-Level 9

Magnetic field at centre of a solenoid is proportional to the current through it. Current through C will be one-third of the current through A. So
Magnetic field at the centre of C = 3/3 = 1T.

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7 months ago

Two cells of emf 2E and E with internal resistance r? and r? respectively are connected in series to an external resistor R (see figure). The value of R, at which the potential difference across the terminals of the first cell becomes zero is:

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Contributor-Level 10

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7 months ago

Physics Class 11th

What will be the average value energy along one degree of freedom for an ideal gas in thermal equilibrium at a temperature T? (kB is Boltzmann constant)

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Physics Work, Energy and Power

Contributor-Level 9

According to principle of equi-partition of Energy, the average energy per molecules associated with each degree of freedom is (1/2)kT.

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7 months ago

A constant power delivering machine has towed a box, which was initially at rest, along a horizontal straight line. The distance moved by the box in time 't' is proportional to:

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Contributor-Level 9

m (dv/dt) = P ⇒ ∫v dv = ∫ (P/m) dt ⇒ v = (2Pt/m)¹/²
⇒ ∫dx = ∫ (2P/m)¹/² t¹/² dt ⇒ x = (2P/m)¹/² (2/3)t³/² ⇒ x ∝ t³/²

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7 months ago

A carrier signal C(t) = 25 sin(2.512 * 10¹⁰t) is amplitude modulated by a message signal m(t) = 5 sin(1.57 * 10⁸t) and transmitted through an antenna. What will be the bandwidth of the modulated signal?

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Physics Physics Ncert Solutions Class 12th

Contributor-Level 10

Frequency of message signal, f? = (1.57 * 10? ) / (2 * 3.14) = 2.5 * 10? Hz
Bandwidth = 2f? = 5 * 10? Hz = 50MHz

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7 months ago

Your friend is having eye sight problem. She is not able to see clearly a distant uniform window mesh and it appears to her non-uniform and distorted. The doctor diagnosed the problems as:

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