Practise Edexcel A-Level Physics electric fields by linking field direction, charge polarity and force on charged or conducting objects.
Some spiders may be seen suddenly moving up into the air, even when there is no wind. This happens when they let out strands of web.
The spiders are pulled upwards as the electrically charged strands of web interact with the Earth's electric field.
The average strength of the Earth's electric field is 120 V m−1 downwards.
State, with a reason, the polarity of the charge on the strands of web.
Negative because the direction of field is direction of force on a positive charge
Or
Field downwards means negatively charged Earth and negative repels negative
Or
Negative because the force is in the opposite direction to the electric field
(1)