An oxide of iron has the formula Fe3O4 and contains both Fe^2+ and Fe^3+ ions. Which one of the following is the fraction of iron ions that are in the…

A 100 % efficient transformer has 1500 turns on its primary coil. The input to the transformer is 250V ac. The output current is 10A and the output power is…

The oscillation period, t, for a spiral spring (weight w, radius R made from wire length l, radius r with a modulus of rigidity n) with a weight W hanging…

The equation connects the variables A, x, y, z, P and Q The following changes are made:x and y are both increased by 50 %z is decreased by 20 %P…

A detector of radioactivity shows background radiation to be 20 counts per minute with no radioactive sources nearby. A radioactive source which emits alpha particles and beta particles is brought…

Element x is in the second period of the Periodic Table. An atom of element y has six moreprotons than an atom of element x. Which statement must be correct?…