RRB NTPC Graduate CBT 1 19 Mar 2026 Shift 2 – Question Paper

Concept: The charge-to-mass ratio ($e/m$) of the electron was measured in cathode-ray experiments.

1. J.J. Thomson (1897) deflected cathode rays with electric and magnetic fields and found $e/m\approx 1.76\times {10}^{11}\text{C/kg}$ – the discovery of the electron.
2. The charge $e$ alone was later measured by Millikan (oil-drop experiment); Bohr gave the atomic model, Einstein the photoelectric explanation.

Yaad rakhein: Thomson $\to e/m$ (and "plum-pudding" model); Millikan $\to e$.

Answer: (D) J.J. Thomson

Concept: If a sum becomes $n$ times itself on simple interest, the interest earned is $(n-1)$ times the principal, so $R=\frac{(n-1)\times 100}{T}$.

1. Amount $=5P$, so $\text{SI}=5P-P=4P$.
2. $R=\frac{\text{SI}\times 100}{P\times T}=\frac{4P\times 100}{P\times 18}=\frac{400}{18}$.
3. $R=22.22\%$ (to two decimal places).

Trick: "$n$ times in $T$ years" on SI $\Rightarrow R\times T=(n-1)\times 100$. Here $R\times 18=400$.

Answer: (C) 22.22

Concept: Decode the expression pair by pair and build the family tree.

1. W – O: W is the brother of O. O x R: O is the wife of R. R + K: R is the son of K. K ÷ G: K is the father of G.
2. So R and G are children of K, i.e. R is G's brother.
3. O is R's wife $=$ G's brother's wife; W is O's brother.
4. Hence W is G's brother's wife's brother.

Trick: Always start from the person asked about at the end (G) and walk back along the chain.

Answer: (A) Brother's wife's brother