Thursday, July 28, 2016

NEET Questions on Electronics



"I object to violence because when it appears to do good, the good is only temporary; the evil it does is permanent"
    – Mahatma Gandhi
Here are three questions on electronics. These were included in the NEET 2016 (July) question paper:
(1) For CE transistor amplifier, the audio signal voltage across the collector resistance of 2 kΩ is 4V. If the current amplification factor of the transistor is 100 and the base resistance is 1 kΩ, then the input signal voltage is
(1) 30 mV
(2) 15 mV
(3) 10 mV
(4) 20 mV
The output signal current ic through the collector resistance Rc is the ratio of output signal voltage vc to the collector resistance Rc:
            ic = vc/Rc = 4V/2 kΩ = 2 mA
The ratio of the collector current to the current amplification factor βac gives the signal current ib in the base circuit:
             ib = ic/βac = 2 mA/100 = 0.02 mA
[Note that βac is the amplification factor for small signal currents]
The input signal voltage vi is the voltage drop across the base resistance Rb due to the base current:
             vi = ibRb = 0.02 mA×1 kΩ = 0.02 volt = 20 mV
[You can obtain the answer in no time if you remember the expression for the voltage gain Av of a common emitter amplifier given by
            Av = vo/vi = βacRo/ri  = 100×(2 kΩ/1kΩ) = 200
Note that Ro is the output resistance and ri is the input resistance.
This gives vi = vo/200 = 4V/200 = 0.02 V = 20 mV]
 (2) The given circuit has two ideal diodes connected as shown in the figure below.
 

The current flowing through the resistance R1 will be
(1) 1.43 A
(2) 3.13 A
(3) 2.5 A
(4) 10.0 A
Since D1 is reverse biased, no current will flow through it. We can therefore forget about the branch containing D1 and R2. The battery sends a current through the series combination of R1 and R3 since the diode D2 is forward biased.
            Current through R1 = 10 V/(2Ω + 2Ω) = 2.5 A

(3) What is the output Y in the following circuit, when all the three inputs A,B,C are first 0 and then 1?

(1) 1,0
(2) 1,1
(3) 0,1
(4) 0.0
When all the three inputs are 0 the NAND gate following the AND gate has both inputs at 0 level. The output Y of the NAND is therefore 1. When all the three inputs are 1, the NAND gate has both inputs at 1 and hence the output is 0. The correct option is (1).


Friday, January 01, 2016

Apply for KEAM 2016

The Commissioner for Entrance Examinations (Govt. of Kerala) has invited applications for the Entrance Examinations for admission to Professional Degree Courses in the State for the year 2016-17. Candidate can apply online on the website of the Commissioner for Entrance Examinations www.cee.kerala.gov.in during the period from 3rd January 2016 to 29th January 2016. The courses offered are:
(a) Medical:
(i) M.B.B.S. (ii) B.D.S. (iii) B.H.M.S. (iv) B.A.M.S. (v) B.S.M.S. (vi) B.U.M.S.
(b) Agriculture:
(i) B.Sc. (Hons.) Agriculture (ii) B.Sc. (Hons.) Forestry
(c) Veterinary:
B.V.Sc. & A.H.
(d) Fisheries:
B.F.Sc.
(e) Engineering:
B.Tech. [including B.Tech. (Agri. Engg.) & B.Tech. (Food Engg.) courses under the Kerala Agricultural University, B.Tech. (Dairy Science & Tech.) & B.Tech. (Food Technology) courses under the Kerala Veterinary & Animal Sciences University]
(f) Architecture:
B.Arch. (No Entrance Examination. Admission is based on merit as assessed by equal weightage to NATA Score and marks/grades in the Qualifying Examination)
The entrance examinations for the above courses will be conducted on 25th, 26th , 27th  and 28th April 2016.
For details you may visit the official website of the commissioner, www.cee.kerala.gov.in

You can access many old questions (with solution) of Kerala Engineering and Medical entrance examinations, by clicking on the label ‘KEAM’ or ‘Kerala’ below this post, so as to become confident in facing the forthcoming exams.

Saturday, December 19, 2015

Apply Online for All India Pre-Medical/Pre-Dental Entrance Test (AIPMT) 2016



You can now apply for All India Pre-Medical/Pre-Dental Entrance Test (AIPMT) 2016.
Application for AIPMT 2016 can be submitted online only and the last date for submitting the application without late fee is 8th January 2016, if you pay the fee using e-challan.
Using other modes of payment you can submit the application without late fee up to 12th January 2016.
The last date for submitting the application with late fee is 6th February 2016, if you pay the fee using e-challan.
Using other modes of payment you can submit the application with late fee up to 10th February 2016.
    The Entrance Test which will be conducted from 10 am to 1 pm on 1st May, 2016 (Sunday) will have one paper with 180 objective type questions from Physics, Chemistry and Biology (Botany & Zoology).
You may visit the AIPMT site at http://aipmt.nic.in for all details.

You can access many old AIPMT questions (with solution) on this site by clicking on the label AIPMT below this post.

Saturday, November 21, 2015

Apply for JEE Main 2016



Joint Entrance Examination (Main) – 2016 [JEE Main 2016] will be conducted on April 3, 2016 (Sunday) (Pen & Paper Based Examination) and on April 9, 2016 (Saturday) & April 10, 2016 (Sunday) (Computer Based Examination).

The aspiring candidates have to apply online only through JEE (Main) website www.jeemain.nic.in.

The online application process will start on 1st December, 2015 and will end on 31st December, 2015.

You may visit the JEE Main site www.jeemain.nic.in for complete information.