Hi,
I observed the following phenomenon when using Oscilloscope(Tekronix TDS 2024B) to measure the output voltage of function generator(Agilent 33250A).

1. connect both leads of function generator to the oscilloscope probe and ground clip, ideal sine wave 10 Hz is observed.
2. Only connect positive lead to the oscilloscope probe, a 60Hz signal is superimposed on the the 10Hz signal.
3. Only connect negative lead to the oscilloscope probe, a 60Hz signal is observed.
Things I know, 1. the 60Hz signal is electric supply. 2. The oscilloscope measures the potential difference between probe and ground clip which is the ground.
My questions are,
1. why the negative lead has a voltage of 60Hz, is it just due to the electric-magnetic field in the air?
2. In the first image, may I say that although the negative lead has a voltage over ground(from last image), when the it is connected to the ground clip, the voltage on it is forced to be zero?
I observed the following phenomenon when using Oscilloscope(Tekronix TDS 2024B) to measure the output voltage of function generator(Agilent 33250A).

1. connect both leads of function generator to the oscilloscope probe and ground clip, ideal sine wave 10 Hz is observed.
2. Only connect positive lead to the oscilloscope probe, a 60Hz signal is superimposed on the the 10Hz signal.
3. Only connect negative lead to the oscilloscope probe, a 60Hz signal is observed.
Things I know, 1. the 60Hz signal is electric supply. 2. The oscilloscope measures the potential difference between probe and ground clip which is the ground.
My questions are,
1. why the negative lead has a voltage of 60Hz, is it just due to the electric-magnetic field in the air?
2. In the first image, may I say that although the negative lead has a voltage over ground(from last image), when the it is connected to the ground clip, the voltage on it is forced to be zero?