Python Turtle: Draw concentric circles using circle() method

I was showing a grandson patterns drawn with Python's Turtle module, and he asked to see concentric circles. I thought it would be faster to use the turtle's circle() to draw them than to write my own code for generating a circle. Ha! I am stuck. I see that the circle produced begins its circumference at the turtle's current location and its direction of drawing depends on turtle's current direction of motion, but I can't figure out what I need to do to get concentric circles. I am not at this point interested in an efficient way of producing concentric circles: I want to see what I have to do to get this way to work:

def turtle_pos(art,posxy,lift):
    if lift:
        art.penup()
        art.setposition(posxy)
        art.pendown()

def drawit(tshape,tcolor,pen_color,pen_thick,scolor,radius,mv):
    window=turtle.Screen() #Request a screen
    window.bgcolor(scolor) #Set its color

    #...code that defines the turtle trl

    for j in range(1,11):
        turtle_pos(trl,[trl.xcor()+mv,trl.ycor()-mv],1)
        trl.circle(j*radius)

drawit("turtle","purple","green",4,"black",20,30)

You can do it like this:

import turtle

turtle.penup()
for i in range(1, 500, 50):
    turtle.right(90)    # Face South
    turtle.forward(i)   # Move one radius
    turtle.right(270)   # Back to start heading
    turtle.pendown()    # Put the pen back down
    turtle.circle(i)    # Draw a circle
    turtle.penup()      # Pen up while we go home
    turtle.home()       # Head back to the start pos

Which creates the picture below:

Basically it moves the turtle down one radius lenght to keep the center point for all the circles in the same spot.