Two spheres of radius a and b are charged and joined by a wire. The ratio of electric fields due to spheres of radius a and b is

Joined by a wire means they are at the same potential.For same potential kQ1a1=kQ2a2⇒Q1Q2=ab .  Further, the electric field at the surface of the sphere having radius R and charge Q is kQR2.∴E1E2=kQ1/a2kQ2/b2=Q1Q2×b2a2=ba