1 An electric current is the overall movement of charged particles in one direction. 2  To obtain an electric current, there needs to be a continuous circuit from one terminal of a battery to the other. 3  An electric current in a circuit transfers energy from the battery to the circuit components.
A pea gravel walkway or patio costs about $5 per square foot, installed, including a layer of base rock. If you'd like to install it yourself, it will cost half as much.Add in the cost of a header or Bender Board. A wood header is about $5 per linear foot; a metal header is $6 (black metal disappears well).You won't need a header if you're installing gravel against a house, fence, or raised bed.dd in the cost of a header or Bender Board. A wood header is about $5 per linear foot; a metal header is $6 (black metal disappears well). You won't need a header if you're installing gravel against a house, fence, or raised bed.
1 A gravel driveway starts at roughly $0.75 -$3 or more a square foot, or $300 -$1,000 for a 12'x25' single-car driveway. 2  Costs can double for a roadway-quality driveway. 3  Loose gravel will need replenishing periodically, but a correctly designed, installed and maintained gravel driveway can last 50-100 years or more. Macadam typically lasts 6-10 years and provides the decorative and rustic appearance of a gravel driveway but with a firm base. 2  An asphalt driveway costs about $2 -$5 a square foot, or $1,200 -$3,000 for 12'x50' to $31,000 -$75,000 for a 12' lane a quarter mile long.