Identify the type of energy used in each action.

a. electrical energy

b. gravitational potential energy

c. mechanical energy

1. the flexing of an arm muscle

2. a signal transduction process by a neuron

3. a ball at the top of a hill

Explanation:

Electrical energy - The communication of neurons with each other takes place at synapses. Synapses are of two types i.e. chemical and electrical. A signal transduction process by a neuron uses electrical energy.  In electrical synapse, flow of ions between cells takes place.    

Gravitational potential energy  - It is the energy possessed by an object when it is placed at some height. It is given by :

PE = mgh

The energy used when "a ball is at the top of a hill" is gravitational potential energy.

Mechanical energy - It is the total energy i.e. it is the combination of gravitational potential energy and kinetic energy.

The flexing of an arm muscle  is an example of mechanical energy.