Anglican High Prelims 2005 P2 Q5
The figure below shows a paint spray that uses principles in electrostatics.
(a) The pain droplets become positively charged by friction. State where and how the droplets get charged.
(b) This method is sed to apply paint to a grounded metal gate. Explain why the droplets are attracted to the gate.
(c) State and explain another advantage of this method of painting.
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Answer:
(a) Nozzle.
The nozzle is charged positively. When the paint is sprayed, the positive charges are 'brushed' off onto the droplets.
(b) The gate will be induced to a negative charge (as the positively charged spray droplets near).
Since unlike charges attract, the positively charged paint droplets will be attracted to the gate.
(c) The paint will be more evenly distributed because positively charged paint droplets will repel each other.
