Question

The order of the differential equation of all circles of radius r, having centre on y-axis and passing through the origin is

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is A

1

The equation of a family of circles of radius r passing through the origin and having centre on y-axis is $(x-0{)}^2+(y-r{)}^2=r^{2}or{x}^2+y^2-2ry=0,$ This is one parameter family of circles, so its differential equation is of order one.