Final answer:
True, a battery can explode if not jumped correctly. Charging by polarization doesn't require direct contact, so that statement is false. Electric-field lines from a positive charge radiate outward, which is true.
Step-by-step explanation:
A battery can explode if jumped improperly, which is a statement that is true. Jump starting a battery improperly can cause a spark, which may ignite hydrogen gas released by the battery, leading to an explosion.
Charging an object by polarization does not necessarily require touching it with an object carrying excess charge, so the statement is false. Polarization can occur without direct contact, as the electrical field of the charged object can cause a redistribution of charges within the neutral object.
In a photoconductive cell, a current is not created unless a sufficient number of electrons are released to allow a flow of electric charge, hence the statement is false. It often requires multiple photon strikes to dislodge enough electrons to create a measurable current.
The electric-field lines from a positive point charge do indeed spread out radially and point outward, making this statement true.
When discussing batteries, in a closed circuit, the number of electrons leaving the battery is equal to the number of electrons entering it because electric charge is conserved.
Dropping a bar magnet through a copper tube does induce an electric current in the tube due to electromagnetic induction, so this statement is true.
The high-voltage wires that are connected to metal-frame towers are indeed held aloft by insulating connectors, but these wires are not wrapped in insulating material as they are air insulated, making this statement false.