Slide 1 / 25 Slide 2 / 25 1 The induced emf in a closed coil of - PDF document

Slide 1 / 25 Slide 2 / 25 1 The induced emf in a closed coil of wire, according to 2 A changing magnetic field B induces an emf Ɛ in a coil of Faraday’s Law, is proportional to: radius R. What is the induced emf in the coil of radius 2R? I. The magnitude of the magnetic flux II. The magnetic flux density A I A ε III. The number of turns B II B 2ε IV. The rate of change of magnetic flux C II and II C 4ε D III and IV D ε /2 E IV E ε /4 Slide 3 / 25 Slide 4 / 25 3 A uniform magnetic field is distributed in a space of a circle of 4 The number of turns in a long solenoid is doubled, how does radius r. The changing field induces an emf Ɛ in the loop with the inductance of the solenoid change? the radius r. What is the induced emf in the loop with the radius 2r? A It doesn't change B It doubles A ε C It quadruples B 2ε D It is cut to a half C 4ε E It is cut to a quarter D ε /2 E ε /4 Slide 5 / 25 Slide 6 / 25 5 Which of the following is true about the inductors? 6 Which of the following can act as an inductor? I. A long coil I. They store energy over a long time II. A long wire A I A I II. They resist the flow of current III. A conducting sphere B III B III through it C I and II C I and II III. They can produce a magnetic field D II and III D II and III E All of the above E All of the above

Slide 7 / 25 Slide 8 / 25 7 At time t =0 the switch is closed. Which of the following 8 If L is inductance measured in H (Henry), what is 1 H is graphs best describes the voltage V across the resistance R equivalent to? as a function of time t? B A A 1 Vs/A B 1 A/Vs C 1 AV/s D 1 As/V E 1 s/AV D C E Slide 9 / 25 Slide 10 / 25 9 If R is 1 Ω and L is 1 H, then L/R is 10 In the circuit above, what is the instantaneous current at point P after the switch is closed? A 1 V A ε/R B 1 F B 2ε/R C 1 A C ε/2R D 1 C D Lε/R E 1 s E 0 Slide 11 / 25 Slide 12 / 25 11 In the circuit above, what is the current at point P after the 12 The switch is closed for a long time in the circuit above, what switch is closed for a long time? is the energy stored in the inductor? A ε/R A Lε/2R B 2ε/R B Lε 2 /2R 2 C ε/2R C Lε 2 /2R D Lε/R D Lε/2R 2 E 0 E L 2 ε 2 /2R

Slide 13 / 25 Slide 14 / 25 13 An electric circuit consists of a battery of emf Ɛ, a resistor R 14 An electric circuit consists of a battery of emf Ɛ, a resistor R and an inductor L. Which of the following represents the time and an inductor L. The circuit has a time constant τ. When constant? another identical resistor R is connected in parallel to the first one, what is the new time constant? A R/L A τ B RL B 2τ C ε/RL C 4τ D ε/L D τ /2 E L/R E τ /4 Slide 15 / 25 Slide 16 / 25 15 A resistor R, an inductor L and a battery Ɛ are connected in 16 In the circuit above, initially the switch is open and then it is series. Which of the following represents the Kirchhoff’s loop closed at time t =0. What is the current in the resistor at this rule for the given circuit? time? A A 3 A B 1 A B C 0 C D 0.5 A E 0.3 A D E Slide 17 / 25 Slide 18 / 25 17 In the circuit above, the switch has been closed for a long 18 In the circuit above, the switch is closed for a long time. What time, then it is reopened at time t =0. Which of the following is the energy stored in the inductor? graphs best represents the electric current i as a function of time t? A 3 J A B B 6 J C 18 J D 24 J E 36 J D C E

Slide 19 / 25 Slide 20 / 25 19 An inductor of inductance of 2 H is connected in series to a 20 An inductor of inductance of 0.4 H is connected in series to a resistor of 10 Ω and a 12 V battery. What is the time constant resistor of 6 Ω and a 12 V battery. What is the energy stored in of the circuit? the inductor? A 5 s A 0.8 J B 10 s B 1.2 J C 0.2 s C 1.8 J D 0.1 s D 2.4 J E 0.6 s E 3.2 J Slide 21 / 25 Slide 22 / 25 21 In the circuit above, at time t=0 the switch is placed in the 22 In the circuit above, at time t=0 the switch is placed in the position A. What is the current in the resistor at this time? position A. What is the voltage across the resistor at this time? A 0.3 A A 3 V B 0.6 A B 6 V C 0 C 9 V D 3 A D 12 V E 6 A E 0 Slide 23 / 25 Slide 24 / 25 23 In the circuit above, the switch has been kept at the position A 24 In the circuit above, a fully charged capacitor with a for a long time and then at time t=0 is placed at the position B. capacitance C = 25 µF and charge Q = 4 µC is connected to an What is the current in the resistor at this time? inductor L = 10 mH? What is the current in the circuit at the instant when the switch is closed? A 0.3 A A 1 A B 0.6 A B 5 A C 0 C 0 D 3 A D 10 A E 6 A E 15 A

Slide 25 / 25 25 In the circuit above, a fully charged capacitor with a capacitance C = 25 µF and charge Q = 4 µC is connected to an inductor L = 10 mH? Which of the following occurs after the switch is closed? A The charge instantaneously decreases to zero B The charge expotentially decreases to zero C The charge stays unchanged D The charge oscillate with a period of π ms E The charge oscillate with a period of π μs