Protons neutron electrons
The statement that best describes an external circuit is "<span>D. The flow of an alternating current switches direction when a generator's terminals change its charge." The main difference between direct and alternating current is the direction of flow. Direct current follows only one direction from negatve to positive, while alternating current changes direction periodically.</span>
Answer:
B=1.04*10^{-4}T
Explanation:
An infinite wire produces a magnetic field that can be computed with the formula:

where m0 is the magnetic permeability of vacuum (4pi*10^{-7}Tm/A), I is the current of the wire (2.50A) and r is the perpendicular distance to the wire in which B is calculated (3cm=3*10^{-2}m). By replacing we obtain:

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D.4
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Answer:
Both physical and chemical changes
Explanation:
From the definition of the law of conservation of mass, total mass of all the substances taking part in a chemical reaction is conserved and the number of atoms of each element in the reaction does not change when a new product is formed. Both physical and chemical changes follow the law since when the system is closed to all transfers of matter and energy, the mass of the system must remain constant over time, irrespective of the state.