NAEST 2020 Measurement of the voltage and the current using

Question: 1: A Voltmeter, an ammeter, a battery and a resistance (bulb) are connected as shown in the figure. The least count of the ammeter is
एक वोल्टमीटर, एक आमीटर, एक बैटरी तथा एक प्रतिरोध (बल्ब) चित्र में दिखाये अनुसार जोड़े गये हैं। आमीटर का अल्पतमांक है

1. 0.05 A
2. 0.10 A
3. 0.01 A
4. 0.02 A

Question 2: The least count of the voltmeter is
वोल्टमीटर का अल्पतमांक है

1. 0.05 V
2. 0.10 V
3. 0.01 V
4. 0.02 V

Question 3: The ammeter reading is best represented by
आमीटर का पठन इनमें से किससे सबसे अच्छी तरह व्यक्त किया जाता है

1. $0.40 \pm 0.05$ A
2. $0.18 \pm 0.05$ A
3. $0.20 \pm 0.05$ A
4. $0.22 \pm 0.05$ A

Question 4: The voltmeter reading is best represented by
वोल्टमीटर का पठन इनमें से सबसे अच्छी तरह व्यक्त किया जाता है

1. $1.04 \pm 0.05$ V
2. $1.1 \pm 0.05$ V
3. $1.04 \pm 0.01$ V
4. $1.1 \pm 0.1$ V

Solution 1: The ammeter has 20 divisions in 1 A. Thus, its least count is 1/20 = 0.05 A. You cannot measure current with an accuracy better than 0.05 A by using this ammeter. Option (A) is correct.

Solution 2: The voltmeter has 20 divisions in 1 V. Thus, its least count is 1/20 = 0.05 V. You cannot measure voltage with an accuracy better than 0.05 V by using this voltmeter.  Option (A) is correct.

Solution 3: The needle of the ammeter reads 4. Thus, current in the circuit is 4 x 0.05 = 0.20 A. Since the least count of the ammeter is 0.05 A, the measured current shall be reported as $0.20\pm 0.05$ A.  Option (C) is correct.

Solution 4: The needle of the voltmeter reads 1 Volt and 2 points. Thus, the voltage across the voltmeter is 1 + 2 x 0.05 = 1.10 V. Since the least count of the voltmeter is 0.05 V, the measured voltage shall be reported as $1.10\pm 0.05$ V. Option (B) is correct.

Sometimes, the voltmeter reading appears to be 1 Volt and 1 point. In this case, the measured voltage shall be reported as $1.05 \pm 0.05$ V.

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