Two ammeters X and Y have resistances of 1.2 Ω and

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Two ammeters X and Y have resistances of 1.2 Ω and 1.5 Ω respectively and they give full-scale deflection with 150 mA and 250 mA respectively. The ranges have been extended by connecting shunts so as to give full scale deflection with 15 A. The ammeters along with shunts are connected in parallel and then placed in a circuit in which the total current flowing is 15A. The current in amperes indicated in ammeter X is____.

1. 14 to 18
2. 11.12 to 18.20
3. 8.8 to 9.8
4. 9.9 to 10.3

Correct Option: D

For ammeter X, shunt resistance RSX

and,	15 × R_SX	= 150 × 10^-3
	R_SY + 1.2

⇒ R_SX = 0.0121Ω
For ammeter Y, shunt resistance R_SY

	15 × R_SY	= 250 × 10^-3
	R_SY + 1.5

⇒ R_SY = 0.0256Ω
When two ammeters are connected in parallel,

Equivalent resistance of ammeter X,
R_X = R_SX// 1.2Ω = 0.0118 Ω
and equivalent resistance of ammeter Y,
R_Y = R_SY// 1.5 Ω = 0.0245 Ω
The current in amperes indicated in ammeter X,

I₁ = 15 ×	R_Y
	R_X + R_Y

= 15 ×	0.0245	= 10.12 Amp.
	0.245 + 0.0118