Which of the following statements is correct about the forced-draught fan used in steam boilers?
1
The power required by an induced-draught fan is equal to that required by a forced-draught fan for the same amount of draught.
2
The power required by an induced-draught fan is less than that required by a forced-draught fan for the same amount of draught.
3
The power required by an induced-draught fan is greater than that required by a forced-draught fan for the same amount of draught.
4
The power required by an induced-draught fan may be greater than or less than that required by a forced-draught fan for the same amount of draught.