Which statement is not true about electromagnets? A. The electric current in an electromagnet generates a magnetic and electric field surrounding the wire.
B. Electromagnets can be turned off and on. When they are turned off the magnetism disappears.
C. Increasing the voltage of the electromagnet will cause the current to increase, thus increasing the strength of the electromagnet.
D. None of the statements are false

it is a negative acceleration

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures

helium

oxygen

neon

sodium