Current Electricity Quiz 15

Current Electricity Quiz-15

Dear Readers,

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1. When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become?

•  Two times
•  Four times
•  Eight times
•  Sixteen times

Solution
In stretching of wire R∝1/d⁴ , where d= Diameter of wire

Q2. In the given circuit, the potential of the point E is?

•  Zero
•  -8 V
•  -4/3 V
•  4/3 V

Solution
The current in the circuit =8/(5+1)=4/3 Now V_C-V_E=4/3×1⇒V_E=-4/3 V

Q3. An electric fan and a heater are marked as 100 watt,220 volt and 1000 watt,220 volt respectively. The resistance of the heater is?

•  Zero
•  Greater than that of the fan
•  Less than that of the fan
•  Equal to that of the fan

Solution
For constant voltage, we know that P∝1/R So higher the power, lower will be the resistance

Q4. In a thermocouple, the neutral temperature is 270℃ and the temperature of inversion is 525℃. The temperature of cold junction would be?

•  30℃
•  255℃
•  15℃
•  25℃

Solution
15℃

Q5. 5 ampere of current is passed through a metallic conductor. The charge flowing in one minute in coulomb will be?

•  5
•  12
•  1/12
•  300

Solution
 Charge = Current × Time =5×60=300 C

Q6. When the resistance of 9 Ω is connected at the ends of a battery, its potential difference decreases from 40 volt to 30 volt. The internal resistance of the battery is?

•  6 Ω
•  3 Ω
•  9 Ω
•  15 Ω

Solution
The internal resistance of battery is given by r=(E/V-1)R=(40/30-1)×9=(9×10)/30=3Ω

Q7. A wire has a resistance of 6Ω. It is cut into two parts and both half values are connected in parallel. The new resistance is?

•  3 Ω
•  6 Ω
•  12 Ω
•  1.5 Ω

Solution
Resistance of original wire is R=ρ l/A ρ,being the specific resistance of wire. When the wire is cut in two equal halves then resistance becomes R^'=(ρl/2)/A=R/2 Thus, the net resistance of parallel combination of two halves is given by R_net=(R^'×R^')/(R^'+R^' ) = R^'/2=R/(2×2)=6/4=1.5Ω

Q8. A conductor wire having 10²⁹ free electrons/m³ carries a current of 20A. If the cross-section of the wire is 1mm², then the drift velocity of electrons will be?

•  6.25×10^-3 ms^-1
•  1.25×10^-5 ms^-1
•  1.25×10^-3 ms^-1
•  1.25×10^-4 ms^-1

Solution
v_d=I/nAe=20/(10²⁹×10^-6×1.6×10^-19 )=1.25×10^-3 m/s

Q9. Above neutral temperature, thermo e.m.f. in a thermocouple?

•  Decreases with rise in temperature
•  Increases with rise in temperature
•  Remains constant
•  Changes sign

Solution
Decreases with rise in temperature

Q10. The current in the 1Ω resistor shown in the circuit is?

•  2/3 A
•  3 A
•  6 A
•  2 A

Solution
In the given circuit 4Ω resistors are connected in parallel, this combination is connected in series with 1Ω resistance 

∴ 1/R^' =1/4+1/4=2/4=1/2 R^'=2Ω Also, R’’=2 Ω +1Ω =3Ω From Ohm’s law, V=iR ∴ i=V/R=6/3=2A