NUMS MDCAT Past Paper Dated: 2020

21- For gaining an atomic spectra, an evacuated glass tube is filled with:

A. Neon
B. Hydrogen
C. Carbon dioxide
D. Sulphur dioxide

Answer : B. Hydrogen

22- During production of x-rays the cathode and anode are enclosed inside an evacuated glass chamber and high DC voltage of the order of:

A. 1000 V is maintained
B. 10,000 V is maintained
C. 25,000 V is maintained
D. 50,000 V is maintained

Answer : C. 25,000 V is maintained

23- Half-life of iodine-131 is 8 days. If 20mg is present initially, how much iodine is left behind after 2 half-lives?

A. 10 mg
B. 5 mg
C. 2.5 mg
D. 1.25 mg

Answer : B. 5 mg

24- 4.5 × 10⁹ years is the half-life of:

A. U²³⁵
B. U²³⁴
C. U²³⁸
D. C¹⁴

Answer : C. U²³⁸

25- When a charge “Q” on a capacitor is doubled then energy stored “U” will:

A. 2 U
B. 3 U
C. U / 2 
D. 4 U

Answer : D. 4 U

26- By increasing area of the plates and decreasing distance between them, the capacitance of capacitor:

A. Increases
B. Decreases
C. Remains unchanged
D. Depending upon temperature

Answer : A. Increases

27- If we double the separation between two charges then coulomb’s force will become?

A. Doubled
B. Half
C. 4-times
D. 14th

Answer : D. 14th

28- The power of an electric bulb is 100W. It is connected to 110V power supply. The resistance of electric bulb will be?

A. 11 ohm
B. 121 ohm
C. 20 ohm
D. 200 ohm

Answer : B. 121 ohm

29- Terminal voltage “Vi” of the battery is greater than end of the battery when:

A. Battery is charging
B. Battery is discharging
C. Battery is connected with R
D. Battery is connected with voltmeter

Answer : A. Battery is charging

30- The temperature coefficient of semi-conductor is negative because:

A. Resistance increases with increase of temperature
B. Resistance decreases with increase of temperature
C. Resistance decreases with decrease of temperature
D. Resistance remains same with increase of temperature

Answer : B. Resistance decreases with increase of temperature

31- If length of the wire becomes two times to its original value and area becomes one half to its original value then resistance of the wire becomes:

A. Double
B. Four times
C. One half
D. One fourth

Answer : B. Four times

32- The unit of resistivity is:

A. ohm
B. ohm meter
C. ohm / meter
D. meter / ohm

Answer : B. ohm meter

33- 1 kilowatt hour =

A. 1.6 × 10⁻¹⁹ J
B. 3.6 × 10⁵ J
C. 9.1 × 10⁻³¹ J
D. 1.67 × 10⁻²⁷ J

Answer : B. 3.6 × 10⁵ J

34- It is a null type resistance device for measuring potential differences:

A. Galvanometer
B. Ohmmeter
C. Ammeter
D. Potentiometer

Answer : D. Potentiometer

35- Which statement is true about electron affinity?

A. The value of electron affinity is always positive
B. The value of electron affinity is always negative
C. The value of first electron affinity is always positive
D. The value of first electron affinity is always negative

Answer : D. The value of first electron affinity is always negative

36- The bond which is based on attractive forces between oppositely charged ion is:

A. Covalent bond
B. Dative bond
C. Ionic bond
D. Metallic bond

Answer : C. Ionic bond

37- Which statement is incorrect regarding a chemical bond?

A. Bond is formed by the overlapping of half-filled orbitals
B. Bond is formed by the attraction of positive and negative ions
C. Bond is formed by the overlapping of “s” orbital is strong
D. Bond formed by the large sized atoms is strong

Answer : D. Bond formed by the large sized atoms is strong

38- The carbonates of alkali metals are soluble in water except:

A. K₂CO₃
B. Li₂CO₃
C. Na₂CO₃
D. Rb₂CO₃

Answer : B. Li₂CO₃

39- The nitrides of alkaline earth metals hydrolyse with water to form:

A. NH₃
B. H₂
C. N₂
D. NO

Answer : A. NH₃

40- The flame colour of Ca in flame test is:

A. Orange red
B. Golden yellow
C. Red
D. Pink

Answer : A. Orange red

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