Class 12th
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New answer posted
10 months agoContributor-Level 10
For series combination: s = R? + R?
For parallel combination: p = (R? ) / (R? + R? )
Given the condition s = np:
R? + R? = n * (R? ) / (R? + R? )
(R? + R? )² = nR? R?
R? ² + 2R? R? + R? ² = nR? R?
R? ² - 2R? R? + R? ² + 4R? R? = nR? R?
(R? - R? )² = (n - 4)R?
(R? - R? )² / (R? ) = n - 4
n = 4 + (R? - R? )² / (R? )
Since (R? - R? )² is always non-negative, the minimum value of the term (R? - R? )² / (R? ) is 0. This occurs when R? = R?
Therefore, the minimum value of n is 4.
New answer posted
10 months agoContributor-Level 10
The force (F) exerted by radiation is the rate of change of momentum (p).
F = Δp/Δt
For photons, p = E/c. So, F = (1/c) * (ΔE/Δt).
Since Power (P) is ΔE/Δt, F = P/c.
Intensity (I) is Power per unit Area (P/A).
The formula provided in the document is F/A = (nE)/ (Δt c A) which leads to a final calculated value of 25 W/cm².
New answer posted
10 months agoContributor-Level 10
Among its different uses noradrenaline is used as an anti-depressant.
New answer posted
10 months agoContributor-Level 10
ρ = M/V
∴ 6.17 = (2 x MX? ) / (N? x (300 x 10? ¹? )³)
Solving MX? = 50 g
∴ No. of molecules in 200 g
= (200/50) x N? = 4 N?
New answer posted
10 months agoContributor-Level 10
Initial charge Q = CV = 14 * 10? ¹² * 12 = 168 * 10? ¹² C
Initial energy U_in = ½ CV² = ½ (14 * 10? ¹²) * 12² = 1008 pJ
When the battery is disconnected and a dielectric (k=7) is inserted, the new capacitance is C' = kC.
The charge Q remains constant.
Final energy U_f = Q²/2C' = Q²/ (2kC) = (CV)²/ (2kC) = CV²/ (2k)
U_f = (14 * 10? ¹² * 12²) / (2 * 7) = 144 pJ
Mechanical energy available for oscillation
New answer posted
10 months agoContributor-Level 10
For A
0.693/300 = (2.303/t) log (A? /A? )
For B
0.693/180 = (2.303/t) log (B? /B? )
Given A? = B? & A? = 4B?
Substituting & solving we get t = 900 s
New answer posted
10 months agoContributor-Level 10
I = I? sin (ωt) + I? cos (ωt)
This can be written as I = I? sin (ωt + φ), where I? = √ (I? ² + I? ²)
A hot wire ammeter reads the rms value of the current.
I_rms = I? /√2 = √ (I? ² + I? ²)/√2
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