A.) Electromagnetic Current
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To solve this problem it is necessary to apply the kinematic equations of angular motion.
Torque from the rotational movement is defined as

where
I = Moment of inertia
For a disk
Angular acceleration
The angular acceleration at the same time can be defined as function of angular velocity and angular displacement (Without considering time) through the expression:

Where
Final and Initial Angular velocity
Angular acceleration
Angular displacement
Our values are given as






Using the expression of angular acceleration we can find the to then find the torque, that is,




With the expression of the acceleration found it is now necessary to replace it on the torque equation and the respective moment of inertia for the disk, so




Therefore the torque exerted on it is 
Answer:
Option (d) is correct.
Explanation:
Work done is given by :
W = Fd, where F is force and d is displacement
Unit of work done :
The SI unit of force is Newton (N) and that of displacement is meter (m). So, the unit of work done is N-m. It is call Joule. It means that the unit of work done is Joule.
Power is given by rate at which the work is done. It is given by :
P = W/t, W is work done and t is time
Unit of power:
Unit of work is Joule (J) and that of time is second (s). It means that the unit of power is Watt and it is equal to Joule/second
Hence, the correct option is (d) "The unit for work is a joule. The unit for power is a watt, which is a joule per second".
Answer:
0.4 ohms.
Explanation:
From the circuit,
The voltage reading in the voltmeter = voltage drop across each of the parallel resistance.
1/R' = 1/R1+1/R2
R' = (R1×R2)/(R1+R2)
R' = (2.4×1.2)/(2.4+1.2)
R' = 2.88/3.6
R' = 0.8 ohms.
Hence the current flowing through the circuit is
I = V'/R'................ Equation 1
Where V' = voltmeter reading
I = 6/0.8
I = 7.5 A
This is the same current that flows through the variable resistor.
Voltage drop across the variable resistor = 9-6 = 3 V
Therefore, the resistance of the variable resistor = 3/7.5
Resistance = 0.4 ohms.