# Joint Entrance Screening Test (JEST) Past Year Question Papers 2017 Part 5

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Q11. What is the DC base current (approximated to nearest integer value in A) for the following n-p- n silicon transistor circuit, given ?

(a) 20

(b) 24

(c) 16

(d) 32

Q12. Consider a particle confined by a potential , where k is a positive constant. The spectrum of the system, within the WKB approximation is proportional to

(a)

(b)

(c)

(d)

Q13. Consider the Hamiltonian

The time dependent function for and zero for . Find

, where is the normalized ground state of the system at a time and is the state of the system at .

(a)

(b)

(c)

(d)

Q14. The function which exists in the range is periodically repeated between and , where to . Using Fourier series, indicate the correct relation at x = 0

(a)

(b)

(c)

(d)

Q15. A toy car is made from a rectangular block of mass M and four disk wheels of mass m and radii r. The car is attached to a vertical wall by a massless horizontal spring with spring constant k and constrained to move perpendicular to the wall. The coefficient of static friction between the wheel of the car and the floor is . The maximum amplitude of oscillations of the car above which the wheels start slipping is

(a)

(b)

(c)

(d)