JEE Mains · Physics · STD 11 - Units,dimensions and measurement
- JEE Mains 2026
- Hard
- MCQ
Consider the equation \(H = \dfrac{x^p \epsilon^q E^r}{t^s}\), where \(H=\) magnetic field; \(E=\) electric field, \(\epsilon=\) permittivity, \(x=\) distance, \(t=\) time. The values of \(p, q, r\) and \(s\) respectively are:
Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) \(1, 1, 1, 1\)
Step-by-step Solution
Detailed explanation
The dimensional formulas for the given physical quantities are:
Magnetic field intensity \([H] = [M^0 L^{-1} T^0 A^1]\)
Distance \([x] = [M^0 L^1 T^0 A^0]\)
Permittivity \([\epsilon] = [M^{-1} L^{-3} T^4 A^2]\)
Electric field \([E] = [M^1 L^1 T^{-3} A^{-1}]\)
Time \([t] = [M^0 L^0 T^1 A^0]\)
Given the equation \(H = \dfrac{x^p \epsilon^q E^r}{t^s}\), we can write it in terms of dimensions as:
\([M^0 L^{-1} T^0 A^1] = [L]^p [M^{-1} L^{-3} T^4 A^2]^q [M L T^{-3} A^{-1}]^r [T]^{-s}\)
Combining the powers of \(M, L, T\), and \(A\) on the right side:
\([M^0 L^{-1} T^0 A^1] = [M^{-q+r} L^{p-3q+r} T^{4q-3r-s} A^{2q-r}]\)
Equating the powers of corresponding fundamental quantities from both sides:
For \(M\): \(0 = -q + r \implies q = r\)
For \(A\): \(1 = 2q - r\)
Substituting \(r = q\) into the equation for \(A\):
\(1 = 2q - q \implies q = 1\)
Since \(q = r\), we get \(r = 1\).
For \(L\): \(-1 = p - 3q + r\)
Substituting \(q = 1\) and \(r = 1\):
\(-1 = p - 3(1) + 1 \implies -1 = p - 2 \implies p = 1\)
For \(T\): \(0 = 4q - 3r - s\)
Substituting \(q = 1\) and \(r = 1\):
\(0 = 4(1) - 3(1) - s \implies 0 = 1 - s \implies s = 1\)
Thus, the values are \(p = 1\), \(q = 1\), \(r = 1\), and \(s = 1\).
Answer: \(1, 1, 1, 1\)
Magnetic field intensity \([H] = [M^0 L^{-1} T^0 A^1]\)
Distance \([x] = [M^0 L^1 T^0 A^0]\)
Permittivity \([\epsilon] = [M^{-1} L^{-3} T^4 A^2]\)
Electric field \([E] = [M^1 L^1 T^{-3} A^{-1}]\)
Time \([t] = [M^0 L^0 T^1 A^0]\)
Given the equation \(H = \dfrac{x^p \epsilon^q E^r}{t^s}\), we can write it in terms of dimensions as:
\([M^0 L^{-1} T^0 A^1] = [L]^p [M^{-1} L^{-3} T^4 A^2]^q [M L T^{-3} A^{-1}]^r [T]^{-s}\)
Combining the powers of \(M, L, T\), and \(A\) on the right side:
\([M^0 L^{-1} T^0 A^1] = [M^{-q+r} L^{p-3q+r} T^{4q-3r-s} A^{2q-r}]\)
Equating the powers of corresponding fundamental quantities from both sides:
For \(M\): \(0 = -q + r \implies q = r\)
For \(A\): \(1 = 2q - r\)
Substituting \(r = q\) into the equation for \(A\):
\(1 = 2q - q \implies q = 1\)
Since \(q = r\), we get \(r = 1\).
For \(L\): \(-1 = p - 3q + r\)
Substituting \(q = 1\) and \(r = 1\):
\(-1 = p - 3(1) + 1 \implies -1 = p - 2 \implies p = 1\)
For \(T\): \(0 = 4q - 3r - s\)
Substituting \(q = 1\) and \(r = 1\):
\(0 = 4(1) - 3(1) - s \implies 0 = 1 - s \implies s = 1\)
Thus, the values are \(p = 1\), \(q = 1\), \(r = 1\), and \(s = 1\).
Answer: \(1, 1, 1, 1\)
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