A wire 1.0m long and with cross-sectional area 2.0 x 10-7 m2 has a resistance of 0.1\(\Omega\). Calculate the electrical conductivity of the wire

5.0 x 107\(\Omega^{-1} m^{-1}\)

2.0 x 107\(\Omega^{-1} m^{-1}\)

5.0 x 107\(\Omega^{-1} m^{-1}\)

2.0 x 108\(\Omega^{-1} m^{-1}\)

5.0 x 108\(\Omega^{-1} m^{-1}\)

WAEC SSCE - Physics - 2008 (Objective)

Question 1 Report

Control in nuclear reactors is effected with boron rods because rhe rods have the ability to

absorb electrons

absorb neutron

accelerate electrons

slow down neutrons

Answer Details

The control in nuclear reactors is very important to ensure the safety and stability of the reactor. One of the methods used for control is the use of boron rods. These rods are inserted or withdrawn from the reactor core to regulate the nuclear reaction taking place. The reason boron rods are used for control in nuclear reactors is that they have the ability to absorb neutrons. Neutrons are the particles that are responsible for the nuclear reaction that takes place in the core of the reactor. When the boron rods are inserted into the reactor core, they absorb the neutrons and prevent them from interacting with the fuel, which slows down or even stops the nuclear reaction. This ability of boron to absorb neutrons makes it a good material for control rods. The concentration of boron in the rods can be adjusted to control the rate of reaction in the reactor. When the boron rods are withdrawn from the reactor core, fewer neutrons are absorbed, and the nuclear reaction can proceed at a faster rate. So, the answer is "absorb neutron".






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