Question

Gulab Jamuns (assumed to be spherical) are to be heated in an oven. They are available in two sizes, one twice bigger (in radius) than the other. Pizzas (assumed to be discs) are also to be heated in an oven. They are also in two sizes, one twice big (in radius) than the other. All fours are put together to be heated at oven temperature. Choose the correct option from the following:
A. Both gulab jamun will get heated in same time
B. Smaller gulab jamun will heated before the bigger one
C. Smaller pizzas are heated before bigger one
D. Bigger pizzas will heated before smaller one

Answer 1

An oven is an electronic general household item which is used to provide a hot environment for the substances and generally it’s used to cook certain types of foods. An oven works on the principle of conversion of electromagnetic energy into thermal energy. The heating time in an oven of a substance is directly proportional to the surface area of a given substance, we will use this concept to find out which out of given substances will be heated fastest.

Complete answer:
As in an oven, when we put any substance to get cooked and just when we turn on the oven, the electromagnetic radiation produced inside it starts to change in thermal energy which is the cause of the resulting cooked substance that is placed in the oven. Since, this heating time of a substance depends upon the surface area of a substance as, larger the surface area greater the time it will take to cook, lesser the surface area earlier it will cook.

From the given size of Gulab Jamuns the smaller one will have small surface area as compared to larger one and Among the pizzas, the pizza which has a smaller radius which is smaller one will get heated and cooked before the larger one. So, smaller gulab jamun will be heated before the bigger one and smaller pizzas are heated before the bigger one.

Hence, the correct options are B and C.

Note: It should be remembered that, the surface area of a sphere shaped Gulab Jamun of a given radius say $r$ is $4\pi {r^2}$ whereas the surface area of a disc shaped Pizza of radius say $r$ is $\pi {r^2}$ , so we can say that among the gulab jamun and pizza of having same radius $r$ Pizza will get heated earlier than the spherical Gulab Jamun as the surface area of pizza is less than that of Gulab Jamun.