Complete Question 
Find the force that must be exerted on the rod to maintain a constant current of 0.173 A in the resistor.
The figure below shows a zero-resistance rod sliding to the right on two zero-resistance rails separated by the distance L = 0.451 m . The rails are connected by a 
 , and the entire system is in a uniform magnetic field with a magnitude of 0.751 T .
, and the entire system is in a uniform magnetic field with a magnitude of 0.751 T .
 The diagram illustrating this question is shown on the first uploaded image 
Answer:
The value is 

Step-by-step explanation:
 From the question we are told that 
 The current is 

 The length of separation is 

 The resistance is 

 The magnetic field is 

Generally the force is mathematically represented as 
 

Given that the velocity is perpendicular to magnetic field then 

=> 

So 
 

 

 
