Passing exams gives children a sense of satisfaction and happiness, and spurs youngsters on to learn, Michael Gove will say.
Arguing for rigorous testing in England's schools, the Education Secretary is expected to say that easy exams are worse than no exams as they fail to motivate pupils and support those who need it.
He is also expected to defend school league tables, suggesting that they have helped to overcome prejudice against schools in disadvantaged areas.
Mr Gove will tell the Independent Academies Association's conference in north London that "exams matter because motivation matters".
He says: "If we know tests are rigorous, and they require application to pass, then the experience of clearing a hurdle we once considered too high spurs us on to further endeavours and deeper learning."
Mr Gove says that American cognitive scientist Daniel T Willingham has suggested that students are motivated to learn if they enjoy "the pleasurable rush that comes from successful thought".
Issuing a staunch defence of externally-marked tests and league tables, Mr Gove will tell the IAA that "over the last few years, tests have helped overcome prejudice and advance equality."
Mr Gove says that while he is a "huge fan" of teachers marking tests, external exams are "fairer".
"The evidence shows that in teacher assessment of English achievement there is a tendency for ethnic minority children to be under-marked and students from non-minority backgrounds to be more generously marked.
"With external testing there is no opportunity for such bias - the soft bigotry of low expectations - and tests show ethnic minority students performing better. So external tests are not only a way of levelling the playing field for children of all backgrounds, they are a solvent of prejudice."