Answer:
a. the force between them quadruples
Explanation:
The electrostatic force between two charges is given by

where
k is the Coulomb's constant
q1 and q2 are the two charges
r is the separation between the two charges
In this problem, the charges on both objects are doubled, so

While the distance does not change, so the new force will be

so, the force will quadruple.
Answer:
Infinity = Never ending
Explanation:
The universe could be infinite, both in terms of space and time, but there is currently no way to test whether it goes on forever or is just very big. The part of the universe we are able to observe is finite, measuring about 46 billion light years in diameter.
The set of natural numbers is an infinite set. This kind of infinity is, by definition, called countable infinity. All sets that can be put into a bijective relation to the natural numbers are said to have this kind of infinity. This is also expressed by saying that the cardinal number of the set is aleph-naught (ℵ0).
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The complete question is how much heat energy is delivered by the iron in 30 seconds.
Heat is given by IVt, Where I is the current in Amperes, V is the voltage, and t is the time in seconds,
Therefore;
Heat energy = 120 × 10 ×30
= 36000 joules or 36 kJ
Heat energy is measured in joules.