1) A wall socket has current (1) of 3.0 A, and a volt (V) of 120 V. If a vacuum

Question

1) A wall socket has current (1) of 3.0 A, and a volt (V) of 120 V. If a vacuum cleaner i connected to that socket, a back emf ( of 72 V will form from the electric motor a) What is the coil resistance (R) of the electric motor? 2) In a circuit that has two rails. A rod that has a length ) f 0 10 m is moving in a uniformed magnetic field (B) at a speed of 2 5 m/s. The magnetic field (B) has a strength of 0.60 T and the circuit loop has a resistance (R10.030. In the loop an induced current (1) will be created a) What is the force (F) that will act on the moving rod? 3) In the space provided draw a diagram of an incoming ray of light (0) that hits a mirn an angle of 55°. From this pic, show what the outgoing reflective ray (e%) would look like and what would its numerical value equal ? We all know that your homes have primary voltage (V ,) 120 V that comes to them, h most doorbells only need approximately a voltage (V,) of 10 V. This is where a transformer comes into play 4) a) What type of transformer is needed to reduce the voltage? bj What is the turns (N) ratio?

Explanation / Answer

Given

1) I = 3.0 A , V1 = 120 v, emf = 72 V

we know that ohm's law V = I*R ==> R = V/I

here V = V1-emf = 120 -72 = 52 V

R = 52/3 = 17.333 ohm

coil resistance of the electric motor is 17.33 ohm

2) L = 0.10 m , uniform magnetic field B = 0.60 T , speed v = 2.5 m/s

R = 0.030 ohm

induced emf e = B*V*l sin theta , here theta = 90 ( between B and v)

e = 0.60*2.6*0.10 sin90 V = 0.156 V

the induced current i = e/R = 0.156/0.030 A = 5.2 A

now

the force on the moving rod is F = B*I*L sin theta = B*I*L sin 90 = B*I*L = 0.60*5.2*0.10*1 = 0.312 N

3)

we know that if the surface of the mirror is smooth then from the law of reflection

the angle of incidence id equal to angel of reflection theta_i = theta_r

the angle of reflection is = 55 degrees

so that the incident ray , normal and reflected ray all lie in the same plane

4)

Vp = 120 V , Vs = 10 V

to reduce the voltage at the secondary coil the stepdown transformer will be used so that voltage is less and the current will be high

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